CN102420385A - Passive Q-switched microchip laser device - Google Patents

Abstract

The invention discloses a passive Q-switched microchip laser, which belongs to the technical field of lasers. It mainly includes laser gain medium, graphene or carbon nanotube saturable absorber, optical element and LD pumping device. Graphene and carbon nanotube saturable absorbers with a thickness of nanometers are tightly clamped between the laser gain medium and the optical element, and the device coating is used to form a flat cavity or a flat concave cavity, and the glue, optical glue or deepening of the optical glue is used The method fully cured the device into a simple and compact sandwich structure. Using graphene and carbon nanotube materials with wide saturable absorption wavelength range and good thermal conductivity can realize broadband pulse modulation of different wavelengths of microchip lasers and good heat dissipation characteristics. The invention has the advantages of small optical volume, full curing and easy maintenance, and wide wavelength modulation range, can reduce the process difficulty and production cost of pulsed microchip lasers, and has wide application prospects.

Description

Passively Q-switched Microchip Laser

technical field

The invention relates to the field of lasers, in particular to passive Q-switched lasers with a microchip structure and novel saturable absorber materials—graphene and carbon nanotubes.

Background technique

The all-solidified passive Q-switched microchip laser has a simple and compact structure and is easy to maintain. In particular, its extremely short cavity length on the order of millimeters can achieve single-frequency and high-peak-power pulsed laser output, and has high frequency-doubling efficiency. These characteristics make passive Q-switched microchip lasers widely used in scientific research, industrial processing, biomedicine, military detection and other fields. At present, the passively Q-switched microchip laser pumped by LD can realize the pulse output of the pulse width from picosecond to nanosecond, the repetition frequency of the kilohertz level, and the peak power of the kilowatt level. Most passive Q-switched microchip lasers use crystals such as Cr ⁴⁺ :YAG as saturable absorbers, and there are also reports using semiconductor saturable absorber mirrors (SESAM). Even if the former uses bonded Cr ⁴⁺ :YAG/Nd:YAG crystals, there is still the problem that the laser cavity length is not easy to control, and the doping process requirements of this type of crystals are strict, and the damage threshold is not ideal.

As a new type of material, graphene and carbon nanotubes have excellent electrical, optical and mechanical properties, and have important potential application values in high-performance electronic devices, sensing detection, information storage, composite materials and other fields. Graphene and carbon nanotubes have considerable light-limiting effects on multi-wavelength lasers. In particular, graphene materials at the atomic level can achieve saturable absorption from visible light to mid-infrared bands, making them unique in laser manufacturing and applications. unusual significance. With the improvement and maturity of the large-scale production and preparation technology of graphene and carbon nanotube materials, using them as saturable absorbers will be very beneficial to reduce the process difficulty and production cost of pulsed lasers, and is expected to replace the existing laser pulse passive modulation devices.

Contents of the invention

The purpose of the present invention is to use nanoscale thick graphene or carbon nanotube material as a saturable absorber to realize a sandwich-type fully solidified microchip laser with a simple and compact structure and its passive Q-switching at different wavelengths.

To achieve the above object, the present invention adopts the following technical solutions:

Microchip lasers include laser gain media, graphene or carbon nanotube saturable absorbers, optical elements, and LD pumping devices. The graphene or carbon nanotube saturable absorber with nanometer thickness is tightly sandwiched between the laser gain medium and the optical element to form a sandwich structure. Coating the laser gain medium and the optical element as the front and rear cavity mirrors constitutes a parallel plane resonant cavity or a flat concave cavity. The above-mentioned optical elements are devices such as temperature compensation media, frequency doubling crystals, wave plates, optical glass or crystals that pass the oscillation wavelength, or a combination of such devices. Each device is fully cured using gluing, photoresist, or deepening photoresist. The above-mentioned sandwich structure microchip laser is end-pumped by LD or fiber-coupled output LD. The graphene or carbon nanotube saturable absorber contains one or more components of graphene, graphene oxide, graphene polymer, and carbon nanotubes, can be directly grown on the surface of the substrate, and can be prepared as a solid powder Or film form, also can be mixed with PVC and other solvents to prepare polymer film form.

A passively Q-switched microchip laser, comprising a laser gain medium, a graphene or carbon nanotube saturable absorber, an optical element or an optical material, and an LD pumping device; it is characterized in that: a pair of pumps is plated on the pump end face of the gain medium Puguang anti-reflection optical film, or laser total reflection or partial reflection optical film, or the above-mentioned anti-reflection optical film and reflective optical film are coated at the same time; optical components are coated with laser total reflection or partial reflection optical film, using gain media and optical components The coating is used as the front and rear cavity mirrors to form a flat cavity or a flat concave cavity. Graphene and carbon nanotube saturable absorbers with a thickness of 0.5 nm to 5 nm are tightly clamped between the laser gain medium and the optical element to form a sandwich structure.

The prepared graphene or carbon nanotube material saturable absorber has a thickness of 0.5 nanometers to 5 nanometers; the number of graphene material layers in the graphene saturable absorber is 1 to 10 layers.

The laser gain medium is Nd:YAG crystal, Nd:YVO ₄ crystal, Er:Yb:glass laser material.

The optical element is a temperature compensation medium, a frequency doubling crystal, a wave plate, an optical glass or crystal device or material that passes through the oscillation wavelength, and a combination of such devices or materials.

The microchip laser device is fully cured into a sandwich structure by gluing, photoresist or deepening photoresist.

The LD is used for direct end-pumping, and the fiber-coupled output LD is used for end-pumping through the optical system.

The microchip laser of a kind of passive Q-switching is characterized in that: successively comprises LD pumping source 601, collimation system 602, laser gain medium 301 and optical element 402 and graphene or carbon nanotube saturable absorber 201 Closely clamped in the middle to form a sandwich structure; the pump end of the laser gain medium 301 is coated with an optical film that is anti-reflective to the pump light and fully reflective to the laser light, and it cooperates with the optical element 402 coated with an optical film that partially reflects the laser light The front and rear cavity mirrors form a parallel plane resonant cavity or a flat concave cavity.

The fiber-coupled output LD pump source 601 provides pumping, and the pumping light is focused to the pumping end face of the laser gain medium 301 by the collimation system 602 and then coupled and injected; the laser gain medium 301 and the optical element 402 combine the graphene or carbon nanotube saturable The absorber 201 is tightly sandwiched in the middle to form a sandwich structure; the pump end surface of the laser gain medium 301 is coated with an optical film that is anti-reflective to the pump light and fully reflects the laser, and it is in contact with the optical element coated with an optical film that partially reflects the laser. 402 is used as the front and rear cavity mirrors to form a parallel plane resonant cavity or a flat concave cavity; the graphene or carbon nanotube saturable absorber 201 is used as a laser Q-switching device, and the Q-switched pulse laser is output through the optical element 402 .

The microchip laser of a kind of passive Q-switching is characterized in that: it comprises LD pumping source in turn, and LD pumping source 601 is close to laser gain medium 301; Laser gain medium 301 and optical element 402 combine graphene or carbon nano The tube saturable absorber 201 is tightly clamped in the middle to form a sandwich structure; the pump end surface of the laser gain medium 301 is coated with an optical film that is antireflective to the pump light and fully reflective to the laser, and is coated with an optical film that is partially reflective to the laser. The optical element 402 of the film is used as the front and rear cavity mirrors to form a parallel plane resonant cavity or a flat concave cavity.

The LD pumping source 601 is closely attached to the laser gain medium 301 for end pumping; the laser gain medium 301 and the optical element 402 tightly sandwich the graphene or carbon nanotube saturable absorber 201 in the middle to form a sandwich structure; the laser gain medium The pump end surface of 301 is coated with an optical film that is anti-reflective to the pump light and fully reflective to the laser, and is used as a front and rear cavity mirror with the optical element 402 coated with an optical film that partially reflects the laser to form a parallel plane resonant cavity or a flat concave cavity; graphite The alkene or carbon nanotube saturable absorber 201 is used as a laser Q-switching device, and the Q-switched pulsed laser is output through an optical element 402 .

The microchip laser of a kind of passive Q-switching is characterized in that: comprise LD pumping source 601, collimation system 602, partial reflection mirror 603 successively; Laser gain medium 301 and optical element 402 combine graphene or carbon nanotube The saturable absorber 201 is tightly sandwiched in the middle to form a sandwich structure; the pump end surface of the laser gain medium 301 is coated with an optical film that can reduce the reflection of the pump light and partially reflect the laser, which is fully compatible with the laser and the pump light. The reflective optical element 402 forms a resonant cavity.

The LD pump source 601 is coupled and injected into the laser gain medium 301 through the collimation system 602 and the partial reflector 603; the laser gain medium 301 and the optical element 402 tightly clamp the graphene or carbon nanotube saturable absorber 201 in the middle to form a sandwich Structure; the pumping end surface of the laser gain medium 301 is coated with an optical film that increases the transmission of the pump light and partially reflects the laser, which forms a resonant cavity with the optical element 402 that fully reflects the laser and the pump light; graphene or carbon nano The tube saturable absorber 201 is used as a laser Q-switching device, and the Q-switched pulsed laser is reflected from the pump end face of the gain medium and output by the partial reflection mirror 603 .

The present invention adopts the above technical scheme, because the thickness of the saturable absorber of graphene and carbon nanotubes is on the order of nanometers, which hardly affects the length of the resonant cavity, so that the length of the laser resonant cavity formed by coating film only depends on the thickness of the laser gain medium vs. cavity optics thickness. However, the method of gluing, optical glue or deepening optical glue is used to fully cure the microchip laser device into a simple and compact sandwich structure, which can effectively reduce the optical volume of the laser and facilitate maintenance. In particular, graphene and carbon nanotube materials have a wide range of saturable absorption wavelengths, and they can be used as saturable absorbers for passive Q-switching, and suitable laser gain media (eg Nd:YAG, Nd:YVO ₄ , Er: Yb:glass) can realize laser pulse output with different wavelengths. In addition, graphene and carbon nanotube materials have good thermal conductivity, which is very beneficial to the heat conduction and heat dissipation of devices in the cavity. At the same time, the flexible application of various optical devices and their combinations can further realize the characteristics of frequency stabilization, frequency doubling, and polarization of the pulsed laser of the microchip laser.

Description of drawings

Fig. 1 is the structural representation of the first embodiment of the present invention

Fig. 2 is the structural representation of the second embodiment of the present invention

Fig. 3 is the structural representation of the third embodiment of the present invention

Fig. 4 is the structural representation of the fourth embodiment of the present invention

Detailed ways

The present invention will be further described in conjunction with the accompanying drawings and specific embodiments.

The invention mainly includes: laser gain medium, graphene or carbon nanotube saturable absorber, optical element and pumping device.

Specific implementation mode 1

Passively Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) all-solid-state microchip laser with graphene as saturable absorber. As shown in FIG. 2 , the structural devices are LD pump source 601 , optical collimation coupling system 602 , laser gain medium 301 , graphene saturable absorber 201 , and optical element 401 arranged in sequence. In this embodiment, the LD pump source 601 is a fiber-coupled output LD with a wavelength of 808 nm, the laser gain medium 301 is a Nd:YAG crystal, and the graphene saturable absorber 201 is a saturable absorber film with 1 to 10 graphene layers, , the optical element 401 is a YAG crystal. Among them, the laser gain medium 301 and the optical element 401 are coated: S1 is coated with a dichromatic film with a wavelength of 808nm and a total reflection of 1064nm; S2 is coated with a dichromatic film with a wavelength of 808nm and a total reflection of 1064nm; Anti-reflection coating for wavelength 1064nm. S1 and S3 form a parallel plane resonant cavity. The graphene saturable absorber with nanometer thickness and good thermal conductivity is tightly clamped in the laser cavity, and the cavity length only depends on the thickness of the laser gain medium 301 . The above-mentioned laser gain medium 301, graphene saturable absorber 201, and optical element 401 are tightly pressed and optical glue is cured to form a compact sandwich structure, which is naturally cooled by embedding a copper heat sink. The above-mentioned photoresist has high transmittance and low absorptivity for corresponding wavelengths, and has good thermal conductivity, heat resistance and bonding strength. The pump light with a wavelength of 808nm is coupled into the laser gain medium 301 by S1, and the excited laser oscillates in the resonant cavity, modulated by the graphene saturable absorber 201, and then coupled with a pulsed laser with a wavelength of 1064nm at S3.

Specific implementation mode 2

Passively Q-switched neodymium-doped yttrium vanadate crystal (Nd:YVO ₄ ) microchip laser with carbon nanotubes as saturable absorber realizes frequency-doubled green pulse output. As shown in FIG. 2 , the structural device is an LD pump source 601 , an optical collimation coupling system 602 , a laser gain medium 301 , a carbon nanotube saturable absorber 201 , an optical element 401 , and an optical element 402 . In this embodiment, the LD pumping source 601 is a fiber-coupled output LD with a wavelength of 808nm, the laser gain medium 301 is Nd:YVO ₄ crystal, the carbon nanotube saturable absorber 201 is a PVC polymer film of carbon nanotubes, and the optical element 401 is As a temperature compensation medium, the optical element 402 is a KTP frequency doubling crystal. The thermal expansion coefficient or photothermal coefficient of the temperature compensation medium is opposite to that of the Nd:YVO ₄ crystal. Among them, the laser gain medium 301 and the optical element 402 are coated: S1 is coated with a dichromatic film with a wavelength of 808nm and a total reflection of 1064nm; S2 is coated with a dichromatic film with a wavelength of 808nm and a total reflection of 1064nm; Dichroic coating, S4 plated with 1064nm total reflection and 532nm anti-reflection dichroic coating. The carbon nanotube saturable absorber with nanometer thickness and good thermal conductivity is tightly sandwiched between the laser gain medium 301 and the optical element 401. S1 and S3 form a flat resonant cavity. The length of the laser cavity only depends on the laser gain medium 301 and the thickness of the optical element 401. S3 and S4 form a frequency doubling cavity. The above-mentioned laser gain medium 301, carbon nanotube saturable absorber 201, optical element 401, and optical element 402 are tightly pressed and optical glue is cured into a compact complex sandwich structure, which is naturally cooled by embedding a copper heat sink. The above-mentioned photoresist has high transmittance and low absorptivity for corresponding wavelengths, and has good thermal conductivity, heat resistance and bonding strength. The pump light with a wavelength of 808nm is coupled into the laser gain medium 301 by S1, and the excited laser oscillates in the resonant cavity, modulated by the carbon nanotube saturable absorber 201, and then coupled with pulsed laser light with a wavelength of 1064nm at S3. During this period, the deformation of the device in the cavity caused by the thermal effect is corrected by the optical element 401, so that the laser cavity length is not sensitive to temperature, thereby obtaining a frequency stabilization effect. Thereafter, frequency doubling is provided by the optical element 402, and pulsed laser output with a wavelength of 532 nm is realized in S4.

Specific implementation mode 3

Graphene as saturable absorber for passive Q-switching of Er:Yb:glass all-solidified microchip lasers. As shown in FIG. 3 , the structural device is an LD pump source 601 , a laser gain medium 301 , a graphene saturable absorber 201 , and an optical element 401 arranged in sequence. In the present embodiment, the LD pumping source 601 is an LD with a wavelength of 980nm, the laser gain medium 301 is Er:Yb:glass material, and the graphene saturable absorber 201 is a single-layer graphene grown on the optical element 401, and the optical element 401 It is 6H-SiC crystal. Wherein, the pumping end surface of the laser gain medium 301 is coated with a dichroic film with a wavelength of 980nm for anti-reflection and 1550nm for total reflection. Since the 6H-SiC crystal itself has a relatively high refractive index (n=2.6), the reflectivity of the optical element is 20%, and together with the pumping end face of the laser gain medium 301, it forms a parallel plane resonant cavity. Graphene is directly grown on the inner surface of the cavity of the optical element 401 as a saturable absorber. The LD pumping source 601 is close to the pumping end face of the laser gain medium 301 for direct end face pumping. The above devices are tightly pressed and photoresist is cured into a compact sandwich structure, which is naturally cooled by embedding a copper heat sink. The above-mentioned photoresist has high transmittance and low absorptivity for corresponding wavelengths, and has good thermal conductivity, heat resistance and bonding strength. The 980nm excitation light is coupled in through the pump end face of the laser gain medium 301, and the generated laser oscillates in the flat cavity, and is modulated by the graphene saturable absorber 201, and the optical element 401 couples out a pulsed laser with a wavelength of 1550nm.

Specific implementation mode 4

Graphene as saturable absorber to achieve passive Q-switched YLF matrix epitaxial growth LiYErTmHoF crystal fully solidified microchip laser. As shown in FIG. 1 , the structural device is a pump source 601 , an optical collimation coupling system 602 , a partial mirror 603 , a laser gain medium 301 , a graphene saturable absorber 201 , and an optical element 401 arranged in sequence. In this embodiment, the pump source 601 is a krypton laser with a wavelength of 647nm, the laser gain medium 301 is a LiYErTmHoF crystal epitaxially grown on a YLF matrix, the graphene saturable absorber 201 is graphene oxide powder, and the optical element 401 is a copper-based gold-plated mirror. Among them, the laser gain medium 301 is coated with anti-reflection and 2um partial reflection dichroic coating on the pump end face of the laser gain medium with a wavelength of 647nm. The partial reflection mirror 603 is coated with anti-reflection and 2um total reflection dichroic film with a wavelength of 647nm. The optical element 401 totally reflects the pumping light and the laser, and forms a flat resonant cavity with the pumping end surface of the laser gain medium 301 . The graphene saturable absorber 201 is tightly clamped in the cavity by the laser gain medium 301 and the optical element 401 . Utilizing the good thermal conductivity of the graphene material, the heat generated by the laser gain medium 301 can be quickly transferred to the optical element 401 to be cooled. The optical element 401, the graphene saturable absorber 201 and the laser gain medium 301 are solidified into a simple and compact sandwich structure by using the deepening photoresist method. The above-mentioned photoresist has high transmittance and low absorptivity for corresponding wavelengths, and has good thermal conductivity, heat resistance and bonding strength. The pump light with a wavelength of 647nm is coupled into the laser gain medium 301 through the partial reflection mirror 603, and the generated laser is oscillated in the cavity and modulated by the graphene saturable absorber 201, and finally coupled and output through the pump end face of the laser gain medium 301, and then passed through The partial reflection mirror 603 reflects the pulse laser with an output wavelength of 2um.

In particular, it is stated that within the spirit and scope of the present invention defined by the appended patent claims, any changes made to the present invention in form and details are within the protection scope of the present invention.

Claims (9)

1. A passively Q-switched microchip laser, comprising laser gain medium, graphene or carbon nanotube saturable absorber, optical element or optical material and LD pumping device; it is characterized in that: the pumping end face of gain medium is plated Anti-reflection optical film for pump light, or total reflection or partial reflection optical film for laser light, or coated with the above-mentioned anti-reflection optical film and reflective optical film at the same time; optical components are coated with total reflection or partial reflection optical film for laser light, using gain medium and The coating of the optical element is used as the front and rear cavity mirrors to form a flat cavity or a flat concave cavity. Graphene and carbon nanotube saturable absorbers with a thickness of 0.5nm to 5nm are tightly clamped between the laser gain medium and the optical element to form a sandwich structure. 2. The microchip laser of a kind of passive Q-switching according to claim 1, is characterized in that: prepared graphene or carbon nanotube material saturable absorber thickness is 0.5 nanometer to 5 nanometers; Graphene saturable absorber The number of layers of graphene material in the body is 1 to 10 layers. 3. A passive Q-switched microchip laser according to claim 1, characterized in that: the laser gain medium is Nd:YAG crystal, Nd:YVO ₄ crystal, Er:Yb:glass laser material. 4. A kind of passive Q-switched microchip laser according to claim 1, characterized in that: the optical element is a temperature compensation medium, a frequency doubling crystal, a wave plate, an optical glass or crystal device or material that passes through the oscillation wavelength, and combinations of such devices or materials. 5. A passively Q-switched microchip laser according to claim 1, characterized in that: the microchip laser device is fully cured into a sandwich structure by gluing, photoglue or deepening photoglue. 6. A passively Q-switched microchip laser according to claim 1, characterized in that: LD is used for direct end-pumping, and optical fiber coupling is used to output LD for end-pumping through an optical system. 7. A kind of microchip laser of passive Q-switching according to claim 1, is characterized in that: comprise LD pumping source (601), collimation system (602), laser gain medium (301) and optical element ( 402) The graphene or carbon nanotube saturable absorber (201) is tightly clamped in the middle to form a sandwich structure; the pump end surface of the laser gain medium (301) is coated with anti-reflection of the pump light and total reflection of the laser An optical film, which is used as a front and rear cavity mirror with an optical element (402) coated with an optical film that partially reflects laser light to form a parallel plane resonant cavity or a flat concave cavity; The fiber-coupled output LD pump source (601) provides pumping, and the pump light is focused to the pump end face of the laser gain medium (301) through the collimation system (602) and coupled and injected; the laser gain medium (301) and the optical element (402 ) tightly sandwich graphene or carbon nanotube saturable absorbers (201) in the middle to form a sandwich structure; the pump end surface of the laser gain medium (301) is coated with an optical film that is anti-reflective to the pump light and fully reflective to the laser , and the optical element (402) coated with an optical film that partially reflects the laser is used as a front and rear cavity mirror to form a parallel plane resonant cavity or a flat concave cavity; a graphene or carbon nanotube saturable absorber (201) is used as a laser Q-switching device, The Q-switched pulse laser is output through an optical element (402). 8. the microchip laser of a kind of passive Q-switching according to claim 1, is characterized in that: comprise LD pumping source successively, LD pumping source (601) is close to laser gain medium (301); Laser gain medium ( 301) and the optical element (402) tightly sandwich the graphene or carbon nanotube saturable absorber (201) in the middle to form a sandwich structure; the pump end surface of the laser gain medium (301) is coated with an anti-reflection layer for the pump light And the optical film for laser total reflection, it and the optical element (402) coated with the optical film for partial reflection of laser are used as front and rear cavity mirrors to form a parallel plane resonant cavity or a flat concave cavity; The LD pump source (601) is close to the laser gain medium (301) for end pumping; the laser gain medium (301) and the optical element (402) tightly clamp the graphene or carbon nanotube saturable absorber (201) In the middle, a sandwich structure is formed; the pump end surface of the laser gain medium (301) is coated with an optical film that is anti-reflective to the pump light and fully reflective to the laser light, and it cooperates with the optical element (402) coated with an optical film that partially reflects the laser light. The front and rear cavity mirrors form a parallel plane resonant cavity or a flat concave cavity; the graphene or carbon nanotube saturable absorber (201) is used as a laser Q-switching device, and the Q-switched pulse laser is output through an optical element (402). 9. The microchip laser of a kind of passive Q-switching according to claim 1, is characterized in that: comprise LD pumping source (601), collimation system (602), partial reflection mirror (603) successively; Laser gain medium (301) and the optical element (402) tightly sandwich the graphene or carbon nanotube saturable absorber (201) in the middle to form a sandwich structure; the pump end surface of the laser gain medium (301) is coated with An optical film that is anti-reflection and partially reflects the laser light, and forms a resonant cavity with the optical element (402) that fully reflects the laser light and the pump light; The LD pump source (601) is coupled and injected into the laser gain medium (301) through the collimation system (602) and the partial reflection mirror (603); the laser gain medium (301) and the optical element (402) combine graphene or carbon nanotubes The saturable absorber (201) is tightly clamped in the middle to form a sandwich structure; the pump end surface of the laser gain medium (301) is coated with an optical film that can enhance the reflection of the pump light and partially reflect the laser, which is compatible with the laser and the pump. The optical element (402) of total light reflection constitutes a resonant cavity; the graphene or carbon nanotube saturable absorber (201) is used as a laser Q-switching device, and the Q-switched pulsed laser is reflected from the pump end face of the gain medium through a partial reflector (603) output.

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