CN108649427A - Efficient lasing output DFB semiconductor laser device and integreted phontonics transmitting chip - Google Patents

Abstract

The invention discloses a high-efficiency lasing output DFB semiconductor laser device and a photon integrated emission chip. The frequency-selective grating of the laser device is an ordinary uniform grating or uniform sampling grating, which has two mutually electrically isolated electrodes, one end face of the laser is coated with a high reflection film, and the other end face is coated with an anti-reflection film or other Anti-reflection measures. The invention improves the efficiency of the effective lasing output laser of the laser while reducing the threshold value of the laser; by changing the size or ratio of the injection current in the phase shift area and the feedback area, the continuous The single-mode lasing of the laser is adjusted and the lasing wavelength meets the requirements of the ITU-T standard. If the total operating current and operating temperature remain unchanged, the ratio of injection current in the phase shift region and the feedback region of the laser is changed, so that when the laser is single-mode lasing and the wavelength is continuously adjustable, the output power of the laser will fluctuate very little.

Description

High-efficiency lasing output DFB semiconductor laser device and photonic integrated emission chip

technical field

The invention belongs to the technical field of optoelectronics, and relates to optical fiber communication, photon integration, photoelectric sensing and other photoelectric information processing. The invention relates to a high-efficiency lasing output DFB semiconductor laser device with finely adjustable wavelength within a certain range and a manufacturing method thereof.

Background technique

As the core device of optical fiber communication system, distributed feedback (Distributed Feedback, DFB) semiconductor laser has attracted worldwide attention due to its small size and simple structure. In order to ensure the single-mode yield of DFB semiconductor lasers, it is usually necessary to introduce real phase shift or equivalent phase shift into its frequency-selective grating. In real phase-shift or equivalent phase-shift semiconductor lasers, in order to eliminate the lasing wavelength drift caused by various random factors, wavelength tuning measures should be used to control the lasing wavelength to meet the requirements of ITU-T standards.

If it is a single laser, an additional semiconductor thermoelectric cooler (Thermoelectric Cooler, TEC) can be used to obtain a relatively good lasing wavelength adjustment effect through electrothermal tuning. However, when this kind of electrothermal tuning is used in the monolithic integrated semiconductor laser array of photonic integration circuit (PIC), it is necessary to set up independent thermoelectric temperature control devices for each unit laser, so as to independently adjust each unit laser to align with different ITUs at the same time. -T standard wavelength.

By adjusting the injection current of each unit laser, the lasing wavelength of each unit laser can also be independently controlled to align with different ITU-T standard wavelengths. The disadvantage of using this method is that it will lead to the imbalance of the output laser power of the laser array. The method of adjusting the lasing wavelength to the ITU-T standard by using an electrothermal device or changing the injection current will not only cause a serious imbalance in the output laser power of each unit laser, but also cause an extremely complex structure of the laser array.

Zhou Yating and Chen Xiangfei disclosed a phase-shift electrically controlled sampling grating semiconductor laser and its setting method in the Chinese invention patent No. ZL201210370711.9, and Zhou Yating, Wang Gang and Zhu Hong disclosed it in the Chinese invention patent No. ZL201310078726.2 A phase-shift electrical control DFB semiconductor laser device and its manufacturing method are proposed. The above two patents propose a new distributed feedback semiconductor laser structure. In this laser structure, the frequency-selective grating can be an ordinary uniform grating or Uniform sampling grating, its semiconductor laser structure is composed of two feedback areas and a phase shift area, the electrodes of the two feedback areas can be connected together with wires to form the same feedback area electrode, and control the injection current into the feedback area and the phase shift area Density, you can control the real phase shift or equivalent phase shift introduced in the frequency selective grating of the laser, make the laser single-mode lasing and adjust the relative position of the laser lasing wavelength in the laser channel blocking band, so that in The lasing wavelength of the laser is continuously and finely adjusted within a certain range.

In order to eliminate the adverse effect of the phase of the laser end face on the lasing performance of the laser, the two end faces of the phase shift electrical control distributed feedback laser in the above two patents are usually required to be coated with anti-reflection coatings. When such a laser works, its effective output laser power from one end face is only half of the total laser power, that is to say, its actual effective lasing efficiency is 50%, and the threshold current of the laser is relatively high.

Contents of the invention

Aiming at the above-mentioned shortcomings of semiconductor lasers in the prior art, the present invention proposes a new distributed feedback semiconductor laser structure.

Technical scheme of the present invention:

A high-efficiency lasing output DFB semiconductor laser device, the frequency-selective grating of the high-efficiency lasing output DFB semiconductor laser device is a continuous uniform grating or a uniform sampling grating (one of its ±1-level sub-gratings is selected as a lasing channel) , it has two electrodes that are electrically isolated from each other. One end of the laser is coated with a high-reflection film, which is called a reflective end. The electrode adjacent to the reflective end of the laser is called a phase-shift region electrode. It is called the phase shift area; the other end surface is coated with an anti-reflection film or other anti-reflection measures are taken, which is called the exit end surface, and the electrode adjacent to the exit end surface is called the feedback area electrode, and the corresponding electrode of the feedback area The laser part is called the feedback zone;

As a further improvement of the present invention, electrodes in adjacent phase shift regions and feedback regions are electrically isolated by a certain distance, or by implanting helium ions, or by etching electrical isolation trenches;

As a further improvement of the present invention, the reflectivity of the coating on the reflective end face is >90%, and the reflectance of the coating on the exit end face or the anti-reflection measures is <10%;

As a further improvement of the present invention, the length ratio of the phase shift region and the feedback region is 1:2.

The present invention also provides a distributed feedback semiconductor laser monolithic integrated array. The distributed feedback semiconductor laser monolithic integrated array is composed of the above-mentioned high-efficiency lasing output DFB semiconductor laser device.

The present invention also provides a photonic integrated emission chip, which consists of a laser monitor array, the above-mentioned semiconductor laser monolithic integrated array, a modulator array, a power equalizer array and a multiplexer, which are sequentially grown by selective area epitaxial growth or docking growth technology integrated on the same epitaxial wafer.

The beneficial effects of the present invention are:

When the laser of the present invention is working normally, the distributed phase shift introduced in the laser can be controlled by changing the injection current in the feedback region and the phase shift region, so that the joint effect of the end face phase and the distributed phase shift can be adjusted to make the laser single-mode excitation The lasing wavelength can be continuously and finely adjusted by controlling the relative position of the lasing wavelength in the blocking band of the lasing channel. If the total injection current of the laser remains unchanged, the lasing wavelength of the laser can be finely adjusted by changing the ratio of the injection current in the feedback area and the phase shift area, and the laser maintains a similar threshold value and lasing output power.

Since one end face of the laser is coated with a high-reflection film, and the other end face is coated with an anti-reflection film or other anti-reflection measures are taken, on the one hand, most of the lasing power of the laser can be effectively output, which greatly improves the performance of the laser. The efficiency of effective laser output; on the other hand, the laser self-feedback in the laser cavity is significantly enhanced, which can shorten the length of the laser resonator and greatly reduce the threshold current of the laser compared with both ends of the anti-reflection coating.

If the frequency-selective grating adopts an ordinary uniform grating, under the same operating current, by adjusting the ratio of the injection current in the laser feedback area and the phase shift area, it can ensure that the laser can be continuously and finely lasered within a certain range while single-mode lasing. Adjust the lasing wavelength of the laser to sweep multiple adjacent ITU-T standard wavelengths. In this way, exactly the same lasers can be used to make a laser array to greatly reduce the manufacturing cost of the laser array, and each unit laser in the laser array has a similar threshold current and a balanced laser power output.

If the frequency-selective grating adopts a uniform sampling grating, in the case of the same seed grating, by selecting different sampling periods for the sampling grating, the lasing wavelength can be preliminarily controlled, and by changing the injection current in the feedback area and phase shift area of the laser Or ratio, you can further fine-tune the laser lasing wavelength. Compared with the use of ordinary uniform gratings as frequency-selective gratings, the controllable range of the laser wavelength can be greatly improved. By using such lasers to manufacture laser arrays, multi-wavelength laser arrays with more lasing wavelengths can be manufactured.

Description of drawings

Fig. 1 is the structural representation of laser device of the present invention;

Figure 2 is a schematic diagram of the process of making a uniform grating by double ultraviolet beam interference;

Fig. 3 is a schematic diagram of a process for manufacturing a sampling grating by interference of double ultraviolet light beams passing through a sampling template.

Fig. 4 is a schematic diagram of the functional structure of a multi-wavelength photonic integrated emission chip.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Embodiment one

This embodiment provides a high-efficiency lasing output DFB semiconductor laser device, as shown in Figure 1, its frequency selection grating is a uniform grating or uniform sampling grating, the whole laser is divided into two parts, a phase shift area and a feedback area, and the end face where the phase shift area is located Coated with a high-reflection film, the end face of the feedback area is coated with an anti-reflection film or other anti-reflection measures are taken.

In this embodiment: the electrodes in the phase shift region and the feedback region can be electrically isolated by a certain distance, or by implanting helium ions, or by etching an electrical isolation trench.

The realization principle of the fine adjustment of the lasing wavelength of the high-efficiency lasing output DFB semiconductor laser device of the present invention is as follows:

We take Figure 1 as an example to illustrate. For the sake of simplicity, the lengths of the laser feedback region and the phase shift region are respectively L _P = L, then when the laser feedback region and the phase shift region are injected with different current densities, due to the joint effect of the current thermal effect (playing the main role) and the carrier plasma effect, the effective refractive index of the laser feedback region and the phase shift region n _R and n _P will be different, so in the optical transmission space, the uniform grating of the lasing channel becomes a chirped modulation grating, and the distributed phase shift θ _DPS obtained in the lasing channel can be expressed as

Λ is the grating period of the lasing channel in the feedback area. At the same time, since the end face of the phase shift region is coated with a high-reflection film, there is an end face phase θ _EFPS of any size on this end face of the laser. The joint effect of the distributed phase shift θ _DPS and the end face phase θ _EFPS can be regarded as The lasing channel of the laser introduces a total phase shift θ _total , with

θ _total = θ _DPS + θ _EFPS (2)

θ _always determines the relative position of the lasing wavelength in the forbidden band of the lasing channel. _Changing the size of I _R and IP also changes the size of the distribution phase shift θ _DPS , and correspondingly changes the _total size of the total phase shift θ, which makes the relative position of the lasing wavelength in the forbidden band change. It will switch back and forth between single-mode and dual-mode working states.

If the introduced distributed phase shift θ _DPS is appropriate, the total phase shift θ will _always make the laser work in a single-mode lasing state. At this time, the size of I _R and I _P is continuously changed, and the relative position of the lasing wavelength in the forbidden band will be continuously changed, so that the lasing wavelength of the laser can be finely adjusted continuously.

If the frequency-selective grating is a sampling grating, we usually choose one of its ±1-level sub-gratings as its lasing channel. Assuming that the seed grating period is Λ ₀ and the sampling period is P, then the grating period of the lasing channel is

Formula (1) is still applicable, except that the grating period Λ in formula (1) should be changed to Λ _±1 , and the adjustment effect on the lasing wavelength is still similar when I _R and I _P are changed.

Embodiment two

This embodiment provides a distributed feedback semiconductor laser monolithic integrated array, which is composed of the high-efficiency lasing output DFB semiconductor laser device described in the first embodiment.

This embodiment also provides a kind of photon integrated launch chip (as shown in Figure 4), and this module is by laser monitor array, above-mentioned distributed feedback type semiconductor laser monolithic integrated array, modulator array, power equalizer array and multiplexer , through selective area epitaxial growth or butt growth technology, sequentially grown and integrated on the same epitaxial wafer.

Embodiment Three

This embodiment adopts a manufacturing method of a distributed feedback semiconductor laser and an array thereof, the steps of which are as follows:

(1) Epitaxial n-type InP buffer layer, 100nm thick undoped lattice-matched InGaAsP lower confinement layer, strained InGaAsP multiple quantum wells and 100nm thick p-type lattice-matched InGaAsP upper confinement layer on n-type InP substrate material Floor;

(2) The production method of the grating:

① Manufacturing method of uniform grating: use the method of double-beam holographic interference exposure to record the uniform grating pattern on the photoresist on the upper confinement layer, and then apply material etching to form the required uniform grating on the upper part of the upper confinement layer structure. Fig. 2 is a schematic diagram of the process of making a uniform grating by double ultraviolet light beam interference.

②Uniform sampling grating manufacturing method, using double-beam holographic interference to expose through the sampling photoresist plate, transfer the sampling grating pattern to the photoresist on the upper confinement layer, and then apply material etching, on the upper confinement layer The upper part forms the required sampling grating structure. Fig. 3 is a schematic diagram of a process for manufacturing a sampling grating by interference of double ultraviolet light beams passing through a sampling template.

(3) After the grating is fabricated, the p-type InP layer and the p-type InGaAs ohmic contact layer are grown by secondary epitaxy. After the epitaxial growth is completed, the fabrication of the ridge waveguide is completed by using ordinary photolithography combined with chemical wet etching;

( ₄ ) Deposit a layer of 300nm thick SiO layer or organic BCB insulating layer around the ridge waveguide with plasma enhanced chemical vapor deposition process;

(5) Then use photolithography and chemical wet etching to remove the _SiO2 layer or organic BCB insulating layer above the laser ridge waveguide to expose its InGaAs ohmic contact layer;

(6) Using the magnetron sputtering method, 100nm thick Ti and 400nm thick Au are plated on the entire laser structure, combined with photolithography and chemical wet etching, the InGaAs ohmic contact layer above the ridges A Ti-Au metal P electrode is formed on it;

(7) After thinning the entire laser chip to 150 μm, a 500 nm thick Au-Ge-Ni alloy is evaporated below the base material as an N electrode;

The manufacture of the multi-wavelength laser array chip composed of the unit distributed feedback semiconductor laser of the present invention, compared with the distributed feedback semiconductor laser of a single wavelength, except that one end face is coated with a high reflection film, the other end face is coated with an anti-reflection film or other anti-reflection methods are used. Except for the light measures, the rest of the production process is exactly the same.

In summary, the grating of the high-efficiency lasing output DFB semiconductor laser device of the present invention is a common uniform grating or a uniform sampling grating; an end face of this laser is coated with a high-reflection film, and the electrode adjacent to the end face of the high-reflection film is called a phase shift region Electrodes, the corresponding part of the laser is called the phase shift area; the other end of the laser is coated with an anti-reflection coating or other anti-reflection light-emitting measures, and the electrode adjacent to the end face of the anti-reflection coating or other anti-reflection light-emitting measures is called feedback The corresponding laser part is called the feedback area; the electrodes of the adjacent phase shift area and the feedback area are electrically isolated in some way. By changing the injection current in the feedback area and the phase shift area, the joint effect of the distributed phase shift introduced in the laser and the end face phase can be continuously adjusted, so that the laser can obtain single-mode lasing and continuously finely adjust the lasing wavelength of the laser to meet the ITU-T standard Require. Under the condition that the total operating current of the laser remains constant, the lasing wavelength of the laser can be finely adjusted by changing the ratio of the injection current in the feedback zone and the phase shift zone, and the laser maintains a similar threshold value and lasing output power.

The above is only the preferred mode of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications should also be considered Be the protection scope of the present invention.

Claims (7)

1. High-efficiency lasing output DFB semiconductor laser device, it is characterized in that: the frequency selection grating of described device is along the continuous uniform grating of laser cavity or uniform sampling grating, and it has two mutually electrically isolated electrodes, and an end face of laser is The reflective end face coated with a high-reflection film, the electrode adjacent to the reflective end face of the laser is a phase shift area electrode, and the laser part corresponding to the phase shift area electrode is a phase shift area; the other end face is coated with an anti-reflection film or adopts anti-reflection light output measures The exit end face of the laser beam, the electrode adjacent to the exit end face is the feedback area electrode, and the part of the laser corresponding to the feedback area electrode is the feedback area. 2. The high-efficiency lasing output DFB semiconductor laser device according to claim 1 is characterized in that: between adjacent phase-shifting regions and feedback region electrodes, spacing is provided, or by implanting helium ions, or by etching electrical isolation trenches way of galvanic isolation. 3. The high-efficiency lasing output DFB semiconductor laser device according to claim 1, characterized in that: the reflectance of the reflective end face coating is >90%, and the reflectance of the exit end face coating or anti-reflection measures is <10%. 4. The high-efficiency lasing output DFB semiconductor laser device according to claim 1, characterized in that: the length ratio of the phase shift region and the feedback region is 1:2. 5. A distributed feedback semiconductor laser monolithic integrated array, characterized in that: comprise the high-efficiency lasing output DFB semiconductor laser device described in any one of several claims 1 to 4, each high-efficiency lasing output DFB semiconductor laser device The structure is the same, but by adjusting the size and ratio of the current injected into the phase shift area and the feedback area, the lasing wavelength of each unit laser is finely controlled to align with different ITU-T standards. 6. A monolithic integrated array of distributed feedback semiconductor lasers, characterized in that: comprise the high-efficiency lasing output DFB semiconductor laser device described in any one of claims 1 to 4, each high-efficiency lasing output DFB semiconductor laser device The grating is the same sampling grating as the seed grating; by selecting different sampling periods, the preliminary control of the lasing wavelength of each unit laser is carried out, and the fine control of each unit laser is achieved by adjusting the size and ratio of the current injected into the phase shift area and the feedback area Lasing wavelengths are aligned to different ITU-T standards. 7. A photonic integrated emission chip, characterized in that: by the laser monitor array, the distributed feedback type semiconductor laser monolithic integrated array, modulator array, power equalizer array and multiplexer described in claim 5 or 6, Through selective area epitaxial growth or butt growth, sequential growth is integrated on the same epitaxial wafer.