EP1038342A1 - Method for controlling a unipolar semiconductor laser - Google Patents
Method for controlling a unipolar semiconductor laserInfo
- Publication number
- EP1038342A1 EP1038342A1 EP99947549A EP99947549A EP1038342A1 EP 1038342 A1 EP1038342 A1 EP 1038342A1 EP 99947549 A EP99947549 A EP 99947549A EP 99947549 A EP99947549 A EP 99947549A EP 1038342 A1 EP1038342 A1 EP 1038342A1
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- Prior art keywords
- laser
- unipolar
- optical
- optical control
- control
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- 238000000034 method Methods 0.000 title claims abstract description 39
- 239000004065 semiconductor Substances 0.000 title claims abstract description 39
- 230000003287 optical effect Effects 0.000 claims abstract description 61
- 238000005086 pumping Methods 0.000 claims description 10
- 230000002452 interceptive effect Effects 0.000 claims description 5
- 230000005540 biological transmission Effects 0.000 claims description 2
- 230000005284 excitation Effects 0.000 claims description 2
- 230000004907 flux Effects 0.000 abstract 1
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 19
- 238000005286 illumination Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 230000003247 decreasing effect Effects 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 239000000969 carrier Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 230000006798 recombination Effects 0.000 description 2
- 238000005215 recombination Methods 0.000 description 2
- 238000009877 rendering Methods 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/30—Structure or shape of the active region; Materials used for the active region
- H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
- H01S5/3401—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers having no PN junction, e.g. unipolar lasers, intersubband lasers, quantum cascade lasers
- H01S5/3402—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers having no PN junction, e.g. unipolar lasers, intersubband lasers, quantum cascade lasers intersubband lasers, e.g. transitions within the conduction or valence bands
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
- H01S5/041—Optical pumping
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/0607—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying physical parameters other than the potential of the electrodes, e.g. by an electric or magnetic field, mechanical deformation, pressure, light, temperature
- H01S5/0608—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying physical parameters other than the potential of the electrodes, e.g. by an electric or magnetic field, mechanical deformation, pressure, light, temperature controlled by light, e.g. optical switch
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
- H01S5/1228—DFB lasers with a complex coupled grating, e.g. gain or loss coupling
Definitions
- the field of the invention is that of unipolar semiconductor lasers, which is particularly advantageous for generating wavelengths in the mid-infrared range 4-12 ⁇ m.
- FIG. 1 Such a unipolar laser is produced from a stack of layers of semiconductor materials, of thickness calibrated so as to produce structures with quantum wells having discrete levels of energy.
- This type of laser has already been described in the literature and in particular in the following references: F. Capasso, AY Cho, J. Faist, AL Hutchinson, S. Luryi, C. Sirtori, DL Sivco "Unipolar semiconductor laser" EP 95 302 112.8 .
- Unipolar lasers generally with cascade, involve transitions between discrete levels of energy at the level of the conduction band, that is to say for example between the levels Ei and E 2 illustrated in FIG. 1.
- Energy levels involved in this type of structure thus generate wavelengths in the infrared medium which it is difficult to obtain by other more conventional methods.
- the invention proposes a method for optical control of a unipolar laser.
- This method uses optical beams for controlling wavelengths much shorter than the wavelength of the unipolar laser and therefore of frequency which can be modulated very quickly.
- the subject of the invention is a method for controlling a unipolar semiconductor laser comprising a stack of semiconductor layers so as to create a quantum well structure having in at least one of the semiconductor layers said active layer, at least a first discrete energy level Ei and a second discrete energy level E 2 in the conduction band, so as to create a laser emission, of photonic energy corresponding to the difference in energy levels between said first energy level and said second energy level, under electrical excitation, characterized in that it comprises the optical pumping of said active layer or of another layer of the stack by optical means emitting at least one control beam at a length wave, photonic energy greater than or equal to the band gap of the optically pumped layer.
- semiconductor lasers are lasers having a large number of optical modes as shown in FIG.
- One way of rendering such single-mode lasers is to create at the active layer a diffraction grating whose period fixes the emission wavelength and therefore mode.
- the diffraction grating can be obtained by a grating etched in the structure as illustrated in the article by J. Faist et al. Proceedings of the CLEO conference, 1997.
- the invention proposes to operate the optical control of the unipolar laser with two optical beams capable of interfering with the optically created diffraction grating making it possible to produce a single-mode unipolar laser that is optically controlled and easier to manufacture than that requiring engraving operations.
- the invention also relates to a method of optical control of a unipolar semiconductor laser, characterized in that the optical control means comprise two optical beams of the same wavelength and means for making said beams interfere in the stack of semiconductor layers making up the laser so as to create a network of interference fringes in said stack.
- the network of optical control fringes can be obtained from a single control laser and from means of recombination of said beams, using conventional interference methods.
- FIG. 3 illustrates a first example of an optical control method of a unipolar laser according to the invention
- Figure 4 illustrates the operation of the unipolar laser using the first example of optical control method described in Figure 3;
- FIG. 5 illustrates a second example of an optical control method of a unipolar laser according to the invention
- FIG. 6 illustrates the operation of the unipolar laser using the second example of optical control method described in Figure 5;
- FIG. 7 illustrates a first example of a method according to the invention for rendering a single-pole laser by optical means
- FIG. 8 illustrates a second example of a method according to the invention for making a single-pole laser by optical means
- FIG. 9 illustrates a third example of a method according to the invention making it possible to make a unipolar laser singlemode by optical means
- FIG. 10 illustrates a fourth example of a method according to the invention making it possible to make a unipolar laser singlemode by optical means
- - Figure 11 illustrates a mesa structure of a unipolar semiconductor laser used in the method according to the invention.
- the optical control method of a unipolar semiconductor laser comprises a control laser beam coming to act at the level of the active layer of the quantum structure of the laser or at the level of any layer of the stack of layers. of the laser.
- the wavelength of the control laser beam must be sufficiently low for carriers to be photoinjected above the gap of the semiconductor material forming the layer which it is desired to optically pump into the stack of layers of the unipolar laser.
- the control laser beam emits at a wavelength ⁇ i, associated with a photonic energy h ⁇ i, such as electrons of the valence band BV located on a level of energy E 3 , are injected into the conduction band on the energy level E L
- a photonic energy h ⁇ i such as electrons of the valence band BV located on a level of energy E 3
- the semiconductor laser electrons are brought to the energy level E 2 , then falling to the lower energy level Ei release a photonic energy h ⁇ o corresponding to the emission of the laser at the wavelength ⁇ o associated with the frequency ⁇ 0 .
- Electrons are thus simultaneously brought to the energy level Ei by electrical pumping and optical pumping. This results in a kind of congestion on this energy level and leads to a reduction in the gain of the semiconductor laser.
- FIG. 4 illustrates this type of operation for a structure traversed by a current l 0 where passes from the output power of the laser P 0 (without illumination) to the power Pe (under illumination).
- the control laser beam generates electron-hole pairs in any layer of the stack of layers of the laser, which is not necessarily the active layer. This has the effect of increasing the losses of the laser in this layer by absorption of free carriers, and therefore of decreasing the gain resulting from the laser. The result is therefore the same as in the first variant: By increasing the losses, the net gain of the laser has been decreased, and therefore increased its threshold and decreased its operating power, under control lighting.
- the control laser beam emits at a wavelength ⁇ 2 , associated with a photonic energy h ⁇ 2 , such as electrons of the valence band BV, located on an energy level E 3 is injected into the conduction band on the energy level E 2 .
- the control laser acts as an additional optical pumping which is added to the optical pumping of the unipolar semiconductor laser.
- FIG. 6 The operation of this example of a laser is illustrated in FIG. 6. It appears in particular that in the particular case where the unipolar laser is pumped just below its threshold, the supplement provided by the optical pumping allows the laser to operate, the laser control thus acts as an optical switch of the unipolar laser.
- the wavelength ⁇ u emitted by the unipolar laser is then equal to this period d ⁇ u ⁇ d
- a refractive index of the active layer n 3.3 (classic for ll-V semiconductor materials)
- a tunable unipolar laser is thus obtained, which conventionally is more difficult to obtain in the medium-infrared wavelength range (a few microns).
- Such a laser requires neither a change in operating current, nor a change in temperature, which is a huge advantage for the stability of its performance (in particular the output power), as a function of the wavelength.
- optical devices allowing, from a single optical beam emitted by a control laser, to generate the fringes of illumination.
- These devices include an optical beam separation means into two optical beams and a recombination means according to an interference method.
- FIG. 7 illustrates a first example of a method for optical control of a tunable unipolar laser. This process uses the illumination of the unipolar laser 1, emitting in the direction X, by two optical beams Fi and F 2 coming from a control laser 2 emitting a divergent beam F 0 through a lens 3. More precisely, the incident beam F 0 goes to through a biprism 4 which generates the two interference beams Fi and F 2 .
- FIG. 8 illustrates a second example of an optical control method for a unipolar laser in which the interference is created using two Fresnel mirrors 40 and 41, making an angle between them.
- FIG. 9 illustrates a third example of a method of optical control of a unipolar laser in which the interferences are created two diffraction gratings acting in transmission 42 and 43. It can typically be the same mask locally containing a grating 42 of step di and locally a network 43 of step d 2 .
- FIG. 11 illustrates a structure of a unipolar semiconductor laser in which the emitted light is confined by virtue of an architecture in the form of a mesa, and inside the stack of layers thanks to layers of suitable semiconductor materials.
- the upper electrical contact layer is locally removed over a width of around a few microns. More precisely, FIG. 11 shows an optical opening 10 in the upper contact layer 11.
- the active layer 13 is inserted between different stacks of layers, deposited on the surface of a substrate 12.
- An insulating layer 14 and locally etched allows to transport electrons locally.
- Table 1 refers to all the layers, Table 2 details the active region, Tables 3, 4 and 5 refer to specific stacks determined to obtain the required energy levels. TABLE 1
- GaAs substrate doped n 2-3x10 18 cm -3
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- Engineering & Computer Science (AREA)
- Nanotechnology (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
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Abstract
Description
PROCEDE DE CONTROLE D'UN LASER SEMICONDUCTEUR METHOD FOR CONTROLLING A SEMICONDUCTOR LASER
UNIPOLAIRESINGLE POLE
Le domaine de l'invention est celui des lasers semiconducteurs unipolaires, particulièrement intéressant pour générer des longueurs d'ondes dans le domaine moyen infrarouge 4-12 μm.The field of the invention is that of unipolar semiconductor lasers, which is particularly advantageous for generating wavelengths in the mid-infrared range 4-12 μm.
Le fonctionnement de ce type de laser est illustré en figure 1. Un tel laser unipolaire est réalisé à partir d'un empilement de couches de matériaux semiconducteurs, d'épaisseur calibrée de manière à réaliser des structures à puits quantiques présentant des niveaux discrets d'énergie. Ce type de laser a déjà été décrit dans la littérature et notamment dans les références suivantes : F. Capasso, A. Y. Cho, J. Faist, A.L. Hutchinson, S. Luryi, C. Sirtori, D.L. Sivco « Unipolar semiconductor laser » EP 95 302112.8. J. Faist, F. Capasso, D.L. Sivco, C. Sirtori, AL. Hutchinson, AY. Cho, Quantum cascade laser, Science, vol. 264, p. 553. J. Faist, F. Capasso, C. Sirtori, D.L Sivco, J.N. Baillarjeon, AL. Hutchinson, S.N. G. Chu and A. Y. Cho, « High power mid-infrared (λ ~ 5 μm) quantum cascade laser operating above room température », Appl. Phys. Lett, vol. 68, p. 3680. C. Sirtori, J. Faist, F. Capasso, D.L. Sivco, AL. Hutchinson and AY. Cho, « Quantum cascade laser with plasmon enhanced waveguide operating at 8-4 μm wavelength », Appl. Phys. Lett., vol. 66, p. 3242. Les lasers unipolaires généralement à cascade, mettent en jeu des transitions entre niveaux discrets d'énergie au niveau de la bande de conduction, c'est-à-dire par exemple entre les niveaux Ei et E2 illustrés en figure 1. Lorsqu'un flux d'électrons est injecté dans la structure, il y a émission de photons hυ = E2 - Ei, lors du passage d'électrons du niveau d'énergie E2 au niveau d'énergie EL Les niveaux d'énergie mis en jeu dans ce type de structure génèrent ainsi des longueurs d'onde dans le moyen infrarouge qu'il est difficile d'obtenir selon d'autres méthodes plus classiques.The operation of this type of laser is illustrated in FIG. 1. Such a unipolar laser is produced from a stack of layers of semiconductor materials, of thickness calibrated so as to produce structures with quantum wells having discrete levels of energy. This type of laser has already been described in the literature and in particular in the following references: F. Capasso, AY Cho, J. Faist, AL Hutchinson, S. Luryi, C. Sirtori, DL Sivco "Unipolar semiconductor laser" EP 95 302 112.8 . J. Faist, F. Capasso, DL Sivco, C. Sirtori, AL. Hutchinson, AY. Cho, Quantum laser cascade, Science, vol. 264, p. 553. J. Faist, F. Capasso, C. Sirtori, DL Sivco, JN Baillarjeon, AL. Hutchinson, SNG Chu and AY Cho, "High power mid-infrared (λ ~ 5 μm) quantum cascade laser operating above room temperature", Appl. Phys. Lett, vol. 68, p. 3680. C. Sirtori, J. Faist, F. Capasso, DL Sivco, AL. Hutchinson and AY. Cho, "Quantum cascade laser with plasmon enhanced waveguide operating at 8-4 μm wavelength", Appl. Phys. Lett., Vol. 66, p. 3242. Unipolar lasers generally with cascade, involve transitions between discrete levels of energy at the level of the conduction band, that is to say for example between the levels Ei and E 2 illustrated in FIG. 1. When 'a flow of electrons is injected into the structure, there is emission of photons hυ = E 2 - Ei, during the passage of electrons from energy level E 2 to energy level E L Energy levels involved in this type of structure thus generate wavelengths in the infrared medium which it is difficult to obtain by other more conventional methods.
Actuellement, pour faire du contrôle de puissance sur de tels lasers, voire de la modulation d'amplitude, on utilise un contrôle purement électrique qui consiste à injecter un flux d'électrons plus ou moins important dans ledit laser.Currently, to make power control on such lasers, or even amplitude modulation, a purely electrical control is used which consists in injecting a more or less significant flow of electrons into said laser.
Avec une modulation électrique, il peut être difficile d'obtenir des cadences de modulation très élevées. Les alimentations pouvant commuter rapidement les forts courants d'alimentation de ces lasers sont en effet des alimentations « haut de gamme ».With electrical modulation, it can be difficult to achieve very high modulation rates. Power supplies that can switch quickly, the strong supply currents of these lasers are indeed “high-end” power supplies.
C'est pourquoi l'invention propose un procédé de contrôle optique de laser unipolaire. Ce procédé utilise des faisceaux optiques de contrôle de longueur d'onde beaucoup plus courte que la longueur d'onde du laser unipolaire et donc de fréquence pouvant être modulée très rapidement.This is why the invention proposes a method for optical control of a unipolar laser. This method uses optical beams for controlling wavelengths much shorter than the wavelength of the unipolar laser and therefore of frequency which can be modulated very quickly.
Plus précisément, l'invention a pour objet un procédé de contrôle d'un laser semiconducteur unipolaire comprenant un empilement de couches semiconductrices de manière à créer une structure à puits quantiques présentant dans au moins une des couches semiconductrices dite couche active, au moins un premier niveau discret d'énergie Ei et un second niveau discret d'énergie E2 dans la bande de conduction, de manière à créer une émission laser, d'énergie photonique correspondant à la différence de niveaux d'énergie entre ledit premier niveau d'énergie et ledit second niveau d'énergie, sous excitation électrique, caractérisé en ce qu'il comprend le pompage optique de ladite couche active ou d'une autre couche de l'empilement par des moyens optiques émettant au moins un faisceau de contrôle à une longueur d'onde, d'énergie photonique supérieure ou égale à la bande interdite de la couche pompée optiquement. De manière générale, les lasers semiconducteurs sont des lasers présentant un grand nombre de modes optiques comme le schématise la figure 2. Une façon de rendre de tels lasers monomodes consiste à créer au niveau de la couche active un réseau de diffraction dont la période fixe la longueur d'onde d'émission et donc le mode. Actuellement, le réseau de diffraction peut être obtenu par un réseau gravé dans la structure comme l'illustre l'article de J. Faist et al. Proceedings de la conférence CLEO, 1997.More specifically, the subject of the invention is a method for controlling a unipolar semiconductor laser comprising a stack of semiconductor layers so as to create a quantum well structure having in at least one of the semiconductor layers said active layer, at least a first discrete energy level Ei and a second discrete energy level E 2 in the conduction band, so as to create a laser emission, of photonic energy corresponding to the difference in energy levels between said first energy level and said second energy level, under electrical excitation, characterized in that it comprises the optical pumping of said active layer or of another layer of the stack by optical means emitting at least one control beam at a length wave, photonic energy greater than or equal to the band gap of the optically pumped layer. In general, semiconductor lasers are lasers having a large number of optical modes as shown in FIG. 2. One way of rendering such single-mode lasers is to create at the active layer a diffraction grating whose period fixes the emission wavelength and therefore mode. Currently, the diffraction grating can be obtained by a grating etched in the structure as illustrated in the article by J. Faist et al. Proceedings of the CLEO conference, 1997.
C'est pourquoi, avantageusement l'invention propose d'opérer le contrôle optique du laser unipolaire avec deux faisceaux optiques capables d'interférer le réseau de diffraction créé optiquement permettant de réaliser un laser unipolaire monomode contrôlé optiquement et de fabrication plus aisée que celle nécessitant des opérations de gravure.This is why, advantageously, the invention proposes to operate the optical control of the unipolar laser with two optical beams capable of interfering with the optically created diffraction grating making it possible to produce a single-mode unipolar laser that is optically controlled and easier to manufacture than that requiring engraving operations.
Plus précisément, l'invention a aussi pour objet un procédé de contrôle optique d'un laser semiconducteur unipolaire, caractérisé en ce que les moyens optiques de contrôle comprennent deux faisceaux optiques de même longueur d'onde et des moyens pour faire interférer lesdits faisceaux dans l'empilement de couches semiconductrices composant le laser de manière à créer un réseau de franges d'interférences dans ledit empilement. Selon une variante de l'invention, le réseau de franges optiques de contrôle peut être obtenu à partir d'un unique laser de contrôle et de moyens de recombinaison desdits faisceaux, utilisant des procédés d'interférence classique.More specifically, the invention also relates to a method of optical control of a unipolar semiconductor laser, characterized in that the optical control means comprise two optical beams of the same wavelength and means for making said beams interfere in the stack of semiconductor layers making up the laser so as to create a network of interference fringes in said stack. According to a variant of the invention, the network of optical control fringes can be obtained from a single control laser and from means of recombination of said beams, using conventional interference methods.
L'invention sera mieux comprise et d'autres avantages apparaîtront à la lecture de la description qui va suivre, donnée à titre non limitatif et grâce aux figures annexées parmi lesquelles : - la figure 1 schématise le fonctionnement d'un laser semiconducteur unipolaire, selon l'art connu ;The invention will be better understood and other advantages will appear on reading the description which follows, given without limitation and thanks to the appended figures among which: - Figure 1 shows schematically the operation of a unipolar semiconductor laser, according to known art;
- la figure 2, illustre l'allure des modes optiques obtenus avec un laser unipolaire semiconducteur classique ;- Figure 2 illustrates the appearance of the optical modes obtained with a conventional semiconductor unipolar laser;
- la figure 3 illustre un premier exemple de procédé de contrôle optique d'un laser unipolaire selon l'invention ;- Figure 3 illustrates a first example of an optical control method of a unipolar laser according to the invention;
- la figure 4 illustre le fonctionnement du laser unipolaire utilisant le premier exemple de procédé de contrôle optique décrit en figure 3 ;- Figure 4 illustrates the operation of the unipolar laser using the first example of optical control method described in Figure 3;
- la figure 5 illustre un deuxième exemple de procédé de contrôle optique d'un laser unipolaire selon l'invention ;- Figure 5 illustrates a second example of an optical control method of a unipolar laser according to the invention;
- la figure 6 illustre le fonctionnement du laser unipolaire utilisant le second exemple de procédé de contrôle optique décrit en figure 5 ;- Figure 6 illustrates the operation of the unipolar laser using the second example of optical control method described in Figure 5;
- la figure 7 illustre un premier exemple de procédé selon l'invention pour rendre monomode par un moyen optique un laser unipolaire ;- Figure 7 illustrates a first example of a method according to the invention for rendering a single-pole laser by optical means;
- la figure 8 illustre un second exemple de procédé selon l'invention pour rendre monomode par un moyen optique un laser unipolaire ; - la figure 9 illustre un troisième exemple de procédé selon l'invention permettant de rendre monomode par un moyen optique un laser unipolaire ;- Figure 8 illustrates a second example of a method according to the invention for making a single-pole laser by optical means; FIG. 9 illustrates a third example of a method according to the invention making it possible to make a unipolar laser singlemode by optical means;
- la figure 10 illustre un quatrième exemple de procédé selon l'invention permettant de rendre monomode par un moyen optique un laser unipolaire ; - la figure 11 illustre une structure en mesa d'un laser semiconducteur unipolaire utilisé dans le procédé selon l'invention. De manière générale, le procédé de contrôle optique d'un laser semiconducteur unipolaire, comprend un faisceau laser de contrôle venant agir au niveau de la couche active de la structure quantique du laser ou au niveau d'une couche quelconque de l'empilement de couches du laser. La longueur d'onde du faisceau laser de contrôle doit être suffisamment faible pour que des porteurs soient photoinjectés au-dessus du gap du matériau semiconducteur formant la couche que l'on désire pomper optiquement dans l'empilement de couches du laser unipolaire.FIG. 10 illustrates a fourth example of a method according to the invention making it possible to make a unipolar laser singlemode by optical means; - Figure 11 illustrates a mesa structure of a unipolar semiconductor laser used in the method according to the invention. In general, the optical control method of a unipolar semiconductor laser comprises a control laser beam coming to act at the level of the active layer of the quantum structure of the laser or at the level of any layer of the stack of layers. of the laser. The wavelength of the control laser beam must be sufficiently low for carriers to be photoinjected above the gap of the semiconductor material forming the layer which it is desired to optically pump into the stack of layers of the unipolar laser.
Selon une première variante de l'invention illustrée en figure 3, le faisceau laser de contrôle émet à une longueur d'onde λi, associée à une énergie photonique hυi, telle que des électrons de la bande de valence BV situés sur un niveau d'énergie E3, sont injectés dans la bande de conduction sur le niveau d'énergie EL Par pompage électrique du laser semiconducteur des électrons sont amenés sur le niveau d'énergie E2, puis en tombant au niveau d'énergie inférieur Ei libèrent une énergie photonique hυo correspondant à l'émission du laser à la longueur d'onde λo associée à la fréquence γ0. Des électrons sont ainsi simultanément apportés sur le niveau d'énergie Ei par pompage électrique et pompage optique. Ceci entraîne une sorte d'encombrement sur ce niveau énergétique et conduit à une diminution du gain du laser semiconducteur. Ainsi avec ce type de pompage optique, il est possible de moduler le gain du laser, en diminuant ledit gain. La figure 4 illustre ce type de fonctionnement pour une structure parcourue par un courant l0 où passe de la puissance de sortie du laser P0 (sans éclairement) à la puissance Pe (sous éclairement).According to a first variant of the invention illustrated in FIG. 3, the control laser beam emits at a wavelength λi, associated with a photonic energy hυi, such as electrons of the valence band BV located on a level of energy E 3 , are injected into the conduction band on the energy level E L By electric pumping of the semiconductor laser electrons are brought to the energy level E 2 , then falling to the lower energy level Ei release a photonic energy hυo corresponding to the emission of the laser at the wavelength λo associated with the frequency γ 0 . Electrons are thus simultaneously brought to the energy level Ei by electrical pumping and optical pumping. This results in a kind of congestion on this energy level and leads to a reduction in the gain of the semiconductor laser. Thus with this type of optical pumping, it is possible to modulate the gain of the laser, by reducing said gain. FIG. 4 illustrates this type of operation for a structure traversed by a current l 0 where passes from the output power of the laser P 0 (without illumination) to the power Pe (under illumination).
Selon une autre variante, le faisceau laser de contrôle génère des paires électrons-trous dans une couche quelconque de l'empilement de couches du laser, qui n'est pas nécessairement la couche active. Cela a pour effet d'augmenter les pertes du laser dans cette couche par absorption de porteurs libres, et donc de diminuer le gain résultant du laser. Le résultat est donc le même que dans la première variante : En augmentant les pertes on a diminué le gain net du laser, et donc augmenté son seuil et diminué sa puissance de fonctionnement, sous éclairement de contrôle. Selon une seconde variante de l'invention, illustrée en figure 5, le faisceau laser de contrôle émet à une longueur d'onde λ2, associée à une énergie photonique hυ2, telle que des électrons de la bande de valence BV, situés sur un niveau d'énergie E3 sont injectés dans la bande de conduction sur le niveau d'énergie E2. Dans cette configuration, le gain du laser se trouve amplifié puisque le nombre de transitions d'électrons du niveau d'énergie E2 au niveau d'énergie inférieur Ei est amplifiée. Dans ce cas, le laser de contrôle agit comme un supplément de pompage optique qui s'ajoute au pompage optique du laser semiconducteur unipolaire. Le fonctionnement de cet exemple de laser est illustré en figure 6. Il apparaît notamment que dans le cas particulier où le laser unipolaire est pompé juste en-dessous de son seuil, le supplément apporté par le pompage optique permet au laser de fonctionner, le laser de contrôle agit ainsi comme un interrupteur optique du laser unipolaire. Nous venons de décrire des exemples de procédé de contrôle utilisant un faisceau laser de contrôle. Il peut être particulièrement intéressant d'effectuer le contrôle optique par un réseau de franges optiques pour obtenir un laser unipolaire monomode et dont la longueur d'onde d'émission peut être commandée par le pas du réseau de franges optiques. Pour cela, on réalise des franges de lumière peφendiculaires à la direction longitudinale de la cavité du laser unipolaire.According to another variant, the control laser beam generates electron-hole pairs in any layer of the stack of layers of the laser, which is not necessarily the active layer. This has the effect of increasing the losses of the laser in this layer by absorption of free carriers, and therefore of decreasing the gain resulting from the laser. The result is therefore the same as in the first variant: By increasing the losses, the net gain of the laser has been decreased, and therefore increased its threshold and decreased its operating power, under control lighting. According to a second variant of the invention, illustrated in FIG. 5, the control laser beam emits at a wavelength λ 2 , associated with a photonic energy hυ 2 , such as electrons of the valence band BV, located on an energy level E 3 is injected into the conduction band on the energy level E 2 . In this configuration, the gain of the laser is amplified since the number of electron transitions from the energy level E 2 to the lower energy level Ei is amplified. In this case, the control laser acts as an additional optical pumping which is added to the optical pumping of the unipolar semiconductor laser. The operation of this example of a laser is illustrated in FIG. 6. It appears in particular that in the particular case where the unipolar laser is pumped just below its threshold, the supplement provided by the optical pumping allows the laser to operate, the laser control thus acts as an optical switch of the unipolar laser. We have just described examples of control method using a control laser beam. It may be particularly advantageous to carry out optical control by an array of optical fringes to obtain a single-mode unipolar laser, the emission wavelength of which can be controlled by the pitch of the array of optical fringes. For this, fringes of light are produced peφendicular to the longitudinal direction of the cavity of the unipolar laser.
En effet, la période des franges d est donné classiquement par la formule suivante : d = λc/2 sin φ Si λc est la longueur d'onde du laser de contrôle et ψ l'angle entre chacun des deux faisceaux interférants à la normale de la couche active. La longueur d'onde λu émise par le laser unipolaire est alors égale à cette période d λu ≈ d Par exemple, pour une émission du laser unipolaire à la longueur d'onde λo = 9 μm dans le vide, un indice de réfraction de la couche active n = 3,3 (classique pour les matériaux semiconducteurs ll-V), et des moyens optiques de contrôle émettant deux faisceaux optiques à la longueur d'onde λc = 700 nm l'égalité λu = λo/n = d = λc 2 sin φ, conduit à définir un angle φ = arc sin (n λc/2λo) ce qui donne dans ce cas φ = 7°37, angle qu'il est facile d'obtenir avec des procédés classiques d'interférences qui seront décrits ci- après. Avec ce type de procédé de contrôle utilisant des franges d'éclairement on parvient à réaliser des sources unipolaires accordables en longueur d'onde et ce en changeant la période des franges d'éclairement. Cette période peut être changée en changeant simplement l'angle entre les deux faisceaux ou bien encore en changeant la longueur d'onde du laser de contrôle. Il apparaît en effet que la longueur d'onde du laser unipolaire dans le vide, répond à la formule suivante : λo = nλc/2 sin φIndeed, the period of the fringes d is conventionally given by the following formula: d = λc / 2 sin φ If λc is the wavelength of the control laser and ψ the angle between each of the two interfering beams at the normal of the active layer. The wavelength λu emitted by the unipolar laser is then equal to this period d λu ≈ d For example, for an emission of the unipolar laser at the wavelength λo = 9 μm in vacuum, a refractive index of the active layer n = 3.3 (classic for ll-V semiconductor materials), and optical control means emitting two optical beams at the wavelength λc = 700 nm the equality λu = λo / n = d = λc 2 sin φ, leads to define an angle φ = arc sin (n λc / 2λo) which gives in this case φ = 7 ° 37, angle which is easy d 'Obtain with conventional interference methods which will be described below. With this type of control method using lighting fringes, it is possible to produce unipolar sources tunable in wavelength and this by changing the period of the lighting fringes. This period can be changed by simply changing the angle between the two beams or by changing the wavelength of the control laser. It appears that the wavelength of the unipolar laser in a vacuum corresponds to the following formula: λo = nλc / 2 sin φ
Cela suppose l'emploi d'un laser de contrôle accordable, ce qui est courant dans les domaines de longueur d'onde sub-micronique nécessaires pour le laser de contrôle.This assumes the use of a tunable control laser, which is common in the sub-micron wavelength ranges required for the control laser.
On obtient ainsi un laser unipolaire accordable, ce qui classiquement est plus difficile à obtenir dans le domaine de longueurs d'onde moyen-infrarouge (quelques microns). Un tel laser ne nécessite ni changement de courant de fonctionnement, ni changement de température, ce qui est un avantage énorme pour la stabilité de ses performances (notamment la puissance de sortie), en fonction de la longueur d'onde.A tunable unipolar laser is thus obtained, which conventionally is more difficult to obtain in the medium-infrared wavelength range (a few microns). Such a laser requires neither a change in operating current, nor a change in temperature, which is a huge advantage for the stability of its performance (in particular the output power), as a function of the wavelength.
Nous allons décrire quelques exemples de dispositifs optiques permettant à partir d'un unique faisceau optique émis par un laser de contrôle de générer les franges d'éclairement. Ces dispositifs comprennent un moyen de séparation de faisceau optique en deux faisceaux optiques et un moyen de recombinaison selon un procédé d'interférence.We will describe some examples of optical devices allowing, from a single optical beam emitted by a control laser, to generate the fringes of illumination. These devices include an optical beam separation means into two optical beams and a recombination means according to an interference method.
Dans tous les cas de figures, les franges d'interférences sont réalisées de manière à ce que le pas du réseau ainsi créé soit selon une direction X parallèle à la direction selon laquelle le laser unipolaire émet. La figure 7 illustre un premier exemple de procédé de contrôle optique d'un laser unipolaire accordable. Ce procédé utilise l'illumination du laser unipolaire 1 , émettant selon la direction X, par deux faisceaux optiques Fi et F2 issus d'un laser de contrôle 2 émettant un faisceau divergent F0 au travers d'une lentille 3. Plus précisément, le faisceau incident F0 passe au travers d'un biprisme 4 qui génère les deux faisceaux d'interférences Fi et F2.In all cases, the interference fringes are produced so that the pitch of the network thus created is in a direction X parallel to the direction in which the unipolar laser emits. FIG. 7 illustrates a first example of a method for optical control of a tunable unipolar laser. This process uses the illumination of the unipolar laser 1, emitting in the direction X, by two optical beams Fi and F 2 coming from a control laser 2 emitting a divergent beam F 0 through a lens 3. More precisely, the incident beam F 0 goes to through a biprism 4 which generates the two interference beams Fi and F 2 .
La figure 8 illustre un second exemple de procédé de contrôle optique d'un laser unipolaire dans lequel les interférences sont créées à l'aide de deux miroirs de Fresnel 40 et 41 , faisant un angle entre eux.FIG. 8 illustrates a second example of an optical control method for a unipolar laser in which the interference is created using two Fresnel mirrors 40 and 41, making an angle between them.
La figure 9 illustre un troisième exemple de procédé de contrôle optique d'un laser unipolaire dans lequel les interférences sont créées deux réseaux de diffraction agissant en transmission 42 et 43. Il peut s'agir typiquement d'un même masque contenant localement un réseau 42 de pas di et localement un réseau 43 de pas d2.FIG. 9 illustrates a third example of a method of optical control of a unipolar laser in which the interferences are created two diffraction gratings acting in transmission 42 and 43. It can typically be the same mask locally containing a grating 42 of step di and locally a network 43 of step d 2 .
Il est également possible de réaliser les franges d'interférences à l'aide d'une lame séparatrice 44 et d'un miroir de renvoi 45 comme l'illustre la figure 10 sur un quatrième exemple de procédé.It is also possible to produce the interference fringes using a separating blade 44 and a deflection mirror 45 as illustrated in FIG. 10 on a fourth example of a method.
Dans tous les exemples de procédé de contrôle optique précédemment décrits, il est nécessaire d'illuminer l'empilement de couches du laser unipolaire par le laser de contrôle. Pour cela, il est indispensable d'aménager un accès au niveau de la couche de contact métallique, toujours présente dans un laser semiconducteur qui permet le pompage électrique du laser. La figure 11 illustre une structure de laser unipolaire semiconducteur dans laquelle la lumière émise est confinée grâce à une architecture en forme de mesa, et à l'intérieur de l'empilement de couches grâce à des couches de matériaux semiconducteurs adéquats. La couche supérieure de contact électrique est localement retirée sur une largeur de quelques microns environ. Plus précisément, la figure 11 montre une ouverture optique 10, dans la couche de contact supérieur 11. La couche active 13 est insérée entre différents empilements de couches, déposés à la surface d'un substrat 12. Une couche isolante 14 et localement gravée permet d'assurer localement le transport d'électrons.In all the examples of optical control method described above, it is necessary to illuminate the stack of layers of the unipolar laser by the control laser. For this, it is essential to provide an access at the level of the metallic contact layer, always present in a semiconductor laser which allows the electric pumping of the laser. FIG. 11 illustrates a structure of a unipolar semiconductor laser in which the emitted light is confined by virtue of an architecture in the form of a mesa, and inside the stack of layers thanks to layers of suitable semiconductor materials. The upper electrical contact layer is locally removed over a width of around a few microns. More precisely, FIG. 11 shows an optical opening 10 in the upper contact layer 11. The active layer 13 is inserted between different stacks of layers, deposited on the surface of a substrate 12. An insulating layer 14 and locally etched allows to transport electrons locally.
Les tableaux ci-après décrivent un exemple d'empilement de couches semiconductrices pouvant être utilisé dans un laser de contrôle selon l'invention.The tables below describe an example of a stack of semiconductor layers that can be used in a control laser according to the invention.
Le tableau 1 fait référence à l'ensemble des couches, le tableau 2 détaille la région active, les tableaux 3, 4 et 5 font référence à des empilements particuliers déterminés pour obtenir les niveaux d'énergie requis. TABLEAU 1Table 1 refers to all the layers, Table 2 details the active region, Tables 3, 4 and 5 refer to specific stacks determined to obtain the required energy levels. TABLE 1
n+ GalnAs axIO^cnY3 100A n+ GaAs θxIO^cπV3 7000Λ n AlχGafï.χiAs x * 0.3 0 (top) 6x10' 3 300 An + GalnAs axIO ^ cnY 3 100A n + GaAs θxIO ^ cπV 3 7000Λ n AlχGa fï .χiAs x * 0.3 0 (top) 6x10 ' 3 300 A
i Alo.33Gao.e7As Tableau 4 151 A n GaAs δxIO^cm-3 14000 A n Alo.33Gao.67As (x = 0 *0.3) Tableau 5 6x1 O^rn"3 300 A n Alo.75Gao.25As 6x10 3 6000 A n Alo.33Gao.67As (x = 0.3 -» 0) Tableau 5 6x1017cm"* 300 A n GaAs SxIO^cm"3 3000 A i Alo. 33 Gao.e 7 As Table 4 151 A n GaAs δxIO ^ cm- 3 14000 A n Alo. 33 Gao. 67 As (x = 0 * 0.3) Table 5 6x1 O ^ rn " 3300 A n Alo. 75 Gao. 25 As 6x10 3 6000 A n Alo. 3 3Gao. 67 As (x = 0.3 -» 0) Table 5 6x10 17 cm " * 300 A n GaAs SxIO ^ cm " 3 3000 A
GaAs substrate doped n = 2-3x10 18 cm -3GaAs substrate doped n = 2-3x10 18 cm -3
TABLEAU 2 : Région ActiveTABLE 2: Active Region
i AIGaAs (A1 % = 33) 58 A i GaAs 15 A i AIGaAs (A1 % = 33) 20 A i GaAs 49 A i AIGaAs (A1 % = 33) 17 A i GaAs 40 A i AIGaAs (A1% = 33) 34 A TABLEAU 3i AIGaAs (A1% = 33) 58 A i GaAs 15 A i AIGaAs (A1% = 33) 20 A i GaAs 49 A i AIGaAs (A1% = 33) 17 A i GaAs 40 A i AIGaAs (A1% = 33) 34 A TABLE 3
GaAs 32 AGaAs 32 A
AIGaAs (A1% = 33) 20 AAIGaAs (A1% = 33) 20 A
GaAs 28 A n AIGaAs (A1 % = 33) 23 A n GaAs 4x1017cm-* 23 A n AIGaAs (A1 % = 33) 25 A n GaAs 4x1017cm"3 23 A i AIGaAs (A1 % = 33) 25 A i GaAs 21 AGaAs 28 A n AIGaAs (A1% = 33) 23 A n GaAs 4x10 17 cm- * 23 A n AIGaAs (A1% = 33) 25 A n GaAs 4x10 17 cm "3 23 A i AIGaAs (A1% = 33) 25 A i GaAs 21 A
TABLEAU 4TABLE 4
GaAs 32 AGaAs 32 A
AIGaAs (A1% = 33) 20 AAIGaAs (A1% = 33) 20 A
GaAs 28 AGaAs 28 A
AIGaAs (A1 % = 33) 23 AAIGaAs (A1% = 33) 23 A
GaAs 23 AGaAs 23 A
AIGaAs (A1 % = 33) 25 AAIGaAs (A1% = 33) 25 A
TABLEAU 5TABLE 5
n AIGaAs (A1 % = 33) 12 A n GaAs 48 A n AIGaAs (A1 % = 33) 24 A n GaAs 36 A n AIGaAs (A1 % = 33) 36 A n GaAs 24 A n AIGaAs (A1 % = 33) 48 A n GaAs 12 A n AIGaAs (A1 % = 33) 60 A n AIGaAs (A1% = 33) 12 A n GaAs 48 A n AIGaAs (A1% = 33) 24 A n GaAs 36 A n AIGaAs (A1% = 33) 36 A n GaAs 24 A n AIGaAs (A1% = 33) 48 A n GaAs 12 A n AIGaAs (A1% = 33) 60 A
Claims
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9812812A FR2784514B1 (en) | 1998-10-13 | 1998-10-13 | METHOD FOR CONTROLLING A SINGLE POLE SEMICONDUCTOR LASER |
| FR9812812 | 1998-10-13 | ||
| PCT/FR1999/002457 WO2000022704A1 (en) | 1998-10-13 | 1999-10-12 | Method for controlling a unipolar semiconductor laser |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| EP1038342A1 true EP1038342A1 (en) | 2000-09-27 |
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| Application Number | Title | Priority Date | Filing Date |
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| EP99947549A Ceased EP1038342A1 (en) | 1998-10-13 | 1999-10-12 | Method for controlling a unipolar semiconductor laser |
Country Status (4)
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| US (1) | US6738404B1 (en) |
| EP (1) | EP1038342A1 (en) |
| FR (1) | FR2784514B1 (en) |
| WO (1) | WO2000022704A1 (en) |
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| GB2365620A (en) * | 2000-08-07 | 2002-02-20 | Imperial College | Optical wavelength shifting by semiconductor intersubband laser |
| FR2834130B1 (en) * | 2001-12-20 | 2005-02-18 | Thales Sa | PROCESS FOR IMPROVING THE OPTICAL CHARACTERISTICS OF MULTILAYER OPTOELECTRONIC COMPONENTS |
| DE10227168A1 (en) * | 2002-06-18 | 2004-01-15 | Infineon Technologies Ag | Optical signal transmission device, optical signal transmission method and optical modulator |
| CN1681923B (en) | 2002-07-18 | 2010-06-02 | 孟山都技术有限公司 | Methods for using artificial polynucleotides and compositions thereof to reduce transgene silencing |
| EP2048753B1 (en) * | 2007-10-11 | 2009-11-25 | Alcatel Lucent | Laser module and method of providing a laser module |
| FR2934712B1 (en) * | 2008-08-01 | 2010-08-27 | Thales Sa | METHOD FOR MANUFACTURING AN OPTICAL ANALYSIS DEVICE COMPRISING A QUANTIC CASCADES LASER AND A QUANTUM DETECTOR |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01212487A (en) * | 1988-02-19 | 1989-08-25 | Fujitsu Ltd | Wavelength tunable semiconductor laser |
| US5633512A (en) * | 1990-05-23 | 1997-05-27 | Canon Kabushiki Kaisha | Semiconductor device for varying the mobility of electrons by light irradiation |
| US5166946A (en) * | 1990-10-12 | 1992-11-24 | Martin Marietta Corporation | Apparatus for and method of controlling the emission of a laser |
| US5509025A (en) * | 1994-04-04 | 1996-04-16 | At&T Corp. | Unipolar semiconductor laser |
| US5563902A (en) * | 1994-08-23 | 1996-10-08 | Samsung Electronics, Co. Ltd. | Semiconductor ridge waveguide laser with lateral current injection |
| FR2734097B1 (en) | 1995-05-12 | 1997-06-06 | Thomson Csf | SEMICONDUCTOR LASER |
| FR2736168B1 (en) | 1995-06-30 | 1997-07-25 | Thomson Csf | FREQUENCY CONVERTER COMPRISING A HETEROSTRUCTURE SEMICONDUCTOR GUIDE |
| FR2757684B1 (en) | 1996-12-20 | 1999-03-26 | Thomson Csf | INFRARED DETECTOR WITH QUANTUM STRUCTURE, UNCOOLED |
| US5995529A (en) * | 1997-04-10 | 1999-11-30 | Sandia Corporation | Infrared light sources with semimetal electron injection |
-
1998
- 1998-10-13 FR FR9812812A patent/FR2784514B1/en not_active Expired - Lifetime
-
1999
- 1999-10-12 EP EP99947549A patent/EP1038342A1/en not_active Ceased
- 1999-10-12 WO PCT/FR1999/002457 patent/WO2000022704A1/en active Application Filing
- 1999-10-12 US US09/581,169 patent/US6738404B1/en not_active Expired - Lifetime
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| See references of WO0022704A1 * |
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| WO2000022704A1 (en) | 2000-04-20 |
| US6738404B1 (en) | 2004-05-18 |
| FR2784514A1 (en) | 2000-04-14 |
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