CN116667122A - 1.5 mu m wave band chip-level semiconductor/solid vertical integrated passive Q-switched laser - Google Patents

Abstract

The invention relates to the technical field of passive Q-switched lasers, in particular to a 1.5 μm band chip-level semiconductor/solid vertically integrated passive Q-switched laser, including a pump source, a laser gain medium and a saturable absorber. The pump source adopts VCSEL prepared with microlenses. The pump light emitted by VCSEL is focused by microlenses and enters the laser gain medium for pumping. The pump source and gain medium form a linear three-mirror coupled cavity structure to improve pumping efficiency. The pumped laser gain medium provides optical gain in the 1.5 μm band for the resonator, and after the saturable absorber modulates the intracavity loss of the resonator, the output of passive Q-switched pulses with a wavelength of 1.5 μm is realized. The invention uses a wafer bonding method to realize the vertical integration of chip-level semiconductors/solids among the three components, and the integrated passive Q-switched laser has the advantages of chip-level volume, simple structure, high efficiency, narrow pulse width and high peak power.

Description

1.5μm band chip-scale semiconductor/solid-state vertically integrated passively Q-switched laser

technical field

The invention relates to the technical field of passive Q-switched lasers, in particular to a 1.5 μm band chip-level semiconductor/solid vertically integrated passive Q-switched laser.

Background technique

Passive Q-switching technology is currently one of the most effective methods to obtain miniaturized, high repetition rate, and high peak power laser pulse output. It uses the saturable absorber's nonlinear saturation absorption effect on the light field to control the loss of the resonant cavity, complete the energy storage and release of the working substance, and realize the laser pulse output. It has the advantages of no external drive source control, small size, simple structure, and easy fabrication Low cost and other advantages. The upper energy level lifetime of the solid gain medium is on the order of microseconds to milliseconds, which is several orders of magnitude larger than that of the semiconductor gain medium, and is suitable for the preparation of passive Q-switched lasers with high peak power and short pulse width. However, unlike semiconductor lasers, solid gain media are composed of crystals or glasses and require an external pump source for pumping, making it very challenging to fabricate compact chip-scale high-peak-power lasers.

The 1.5μm band laser has many advantages and has been widely concerned by researchers: (1) The incident energy of the laser in this band is much higher than that of other band lasers, which is considered to be the most ideal eye-safe laser; (2) 1.5μm The band is located in a good atmospheric transmission window, and has strong penetrating ability to smoke and fog, which is especially suitable for field and battlefield environments; (3) This band is also just located in the lowest loss transmission window of silica optical fiber, which is the best for optical fiber communication systems Working wavelength; (4) The 1.5μm band also corresponds to the detection sensitive area of Ge detectors and InGaAs detectors working at room temperature, and the detection and collection of signals can be realized without cryogenic refrigeration. Due to the above-mentioned many advantages, 1.5μm band laser has important application value in civil and military fields such as lidar, laser ranging, remote sensing measurement, optical communication and target recognition. In particular, the rapid development of industries such as drones and unmanned vehicles has made lidar an important research field and hotspot, and new requirements are constantly being put forward for the volume, peak power, repetition frequency and other attributes of the 1.5μm band laser light source.

However, up to now, there are no related reports on chip-scale semiconductor/solid-state vertically integrated lasers in the 1.5 μm band.

Contents of the invention

The object of the present invention is to provide a 1.5 μm band chip-level semiconductor/solid vertically integrated passive Q-switched laser, which has the advantages of chip-level volume, simple structure, high efficiency, narrow pulse width and high peak power.

The 1.5 μm band chip-level semiconductor/solid vertically integrated passive Q-switched laser provided by the present invention includes a pump source, a laser gain medium, and a saturable absorber that are vertically integrated sequentially by wafer bonding; wherein the pump source adopts a vertical cavity For surface-emitting lasers, the emission spectrum of the pump source matches the absorption spectrum of the laser gain medium. Microlenses are prepared on the surface of the vertical-cavity surface-emitting laser. The pump light emitted by the vertical-cavity surface-emitting laser is focused by the microlens and enters the laser. Gain medium; one DBR layer of the vertical cavity surface emitting laser is used as the first reflective layer, the reflectivity of the first reflective layer to the pump light is greater than 99%, and the other DBR layer of the vertical cavity surface emitting laser is used as the second reflective layer , the reflectivity of the second reflective layer to the pump light is between 70% and 98%; the laser gain medium is made of a material that can gain 1.5 μm resonant light; the surface of the laser gain medium facing the vertical cavity surface emitting laser is coated with the second Three reflection layers, the reflection rate of the third reflection layer to the pump light is less than 1% and the reflection rate to the 1.5μm resonant light is greater than 98%; the surface of the laser gain medium facing the saturable absorber is coated with a fourth reflection layer, the first reflection layer The reflectivity of the four reflective layers to the pump light is greater than 98% and the reflectivity to the 1.5μm resonant light is less than 1%; the saturable absorber adopts a material that performs nonlinear saturable absorption on the 1.5μm resonant light; the saturable absorber faces The surface of the laser gain medium is coated with a fifth reflective layer, and the reflectivity of the fifth reflective layer to 1.5 μm resonant light is less than 1%; the surface of the saturable absorber away from the laser gain medium is coated with a sixth reflective layer, and the sixth reflective layer The reflectivity of the 1.5μm resonant light is between 50% and 98%; the third reflective layer and the sixth reflective layer form the resonant cavity of the passive Q-switched laser, which is used to lase the laser with a wavelength of 1.5μm; the first reflective layer, The second reflective layer and the fourth reflective layer form a linear three-mirror coupling cavity, which is used to pump the laser gain medium and provide oscillation gain for the resonator; the F-P interference cavity is formed between the second reflective layer and the fourth reflective layer, which is used to improve The absorption rate of the laser gain medium for the pump light; the pump light emitted by the vertical cavity surface emitting laser enters the laser gain medium after being focused by the microlens, and the pumped laser gain medium provides optical gain for the resonant cavity Vibration is started, and after the intracavity loss of the resonant cavity is modulated by a saturable absorber, a passively Q-switched pulsed laser output with a wavelength of 1.5 μm is realized.

Preferably, the laser gain medium adopts Er ³⁺ doped crystal material, Er ³⁺ doped glass material, Er ³⁺ /Yb ³⁺ co-doped crystal material or Er ³⁺ /Yb ³⁺ co-doped glass material.

Preferably, the saturable absorber adopts Co ²⁺ : MgAl ₂ O ₄ , Cr ²⁺ : ZnS, semiconductor saturable absorbing mirror material, carbon nanotube material, two-dimensional layered material or quantum dot material.

Preferably, the pump light has a wavelength of 976nm.

Preferably, the vertical-cavity surface-emitting laser is a bottom-emitting structure or a top-emitting structure, and the micro The lens is prepared at the light outlet of the vertical cavity surface emitting laser with the bottom emission structure or the top emission structure.

Compared with the prior art, the present invention utilizes the wafer bonding method to realize the vertical integration of the chip-level semiconductor/solid between the pump source, the laser gain medium and the saturable absorber, and the integrated passive Q-switched laser has a chip-level volume, It has the advantages of simple structure, high efficiency, narrow pulse width and high peak power.

Description of drawings

Fig. 1 is a schematic diagram of a combined structure of a 1.5 μm band chip-level semiconductor/solid vertically integrated passive Q-switched laser provided according to Embodiment 1 of the present invention;

2 is a schematic diagram of the exploded structure of a 1.5 μm band chip-level semiconductor/solid vertically integrated passive Q-switched laser provided according to Embodiment 1 of the present invention;

3 is a schematic structural diagram of a 976 nm band VCSEL provided according to Embodiment 1 of the present invention;

4 is a schematic diagram of the optical path of a 1.5 μm band chip-level semiconductor/solid vertically integrated passive Q-switched laser provided according to Embodiment 1 of the present invention;

Fig. 5 is the absorption spectrogram of Er:Yb:YAB crystal provided according to the embodiment of the present invention 1;

6 is an output spectrum diagram of a 1.5 μm band chip-level semiconductor/solid vertically integrated passive Q-switched laser provided according to Embodiment 1 of the present invention;

7 is a schematic diagram of a one-dimensional array of a 1.5 μm band chip-level semiconductor/solid vertically integrated passive Q-switched laser provided according to Embodiment 1 of the present invention;

8 is a schematic diagram of a two-dimensional array of chip-level semiconductor/solid vertically integrated passive Q-switched lasers in the 1.5 μm band according to Embodiment 1 of the present invention.

Reference numerals: pump source 1, first reflective layer 101, second reflective layer 102, microlens 103, active region 104, substrate 105, P-type contact layer 106, N-type contact layer 107, laser gain medium 2 , third reflective layer 201, fourth reflective layer 202, saturable absorber 3, fifth reflective layer 301, sixth reflective layer 302, linear three-mirror coupling cavity 4, resonant cavity 5, pump light 6, resonant light 7 .

Detailed ways

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same blocks are denoted by the same reference numerals. With the same reference numerals, their names and functions are also the same. Therefore, its detailed description will not be repeated.

In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, but not to limit the present invention.

The present invention proposes a 1.5μm band chip-level semiconductor/solid vertically integrated passive Q-switched laser, including a pump source, a laser gain medium and a saturable absorber. The mirror-coupled cavity structure pumps the laser gain medium, and the pumped laser gain medium provides optical gain in the 1.5μm band for the resonator. By designing the appropriate coating parameters of the resonator, the laser with a wavelength of 1.5μm is controlled to vibrate. After saturable absorption After the volume modulates the intracavity loss, the output of passively Q-switched pulsed laser with a wavelength of 1.5 μm is realized.

The pump source, laser gain medium and saturable absorber are vertically integrated at chip level by wafer bonding technology.

The pump source adopts VCSEL (Vertical Cavity Surface Emitting Laser, vertical cavity surface emitting laser). The lens method includes but not limited to thermal reflow, magnetron sputtering, PECVD deposition, focused ion beam etching, limited diffusion wet method, chemical etching method and other methods. The microlens is used to focus the pump light emitted by the VCSEL to improve the pumping efficiency of the pump light, and the microlens is used to achieve the mode matching between the pump light and the resonant light. After the VCSEL emits pump light, it enters the laser gain medium through the microlens integrated on the surface, and uses the linear three-mirror coupling cavity structure to pump the laser gain medium. The emission spectrum of the VCSEL matches the absorption spectrum of the gain crystal (a typical pump The wavelength value is 976nm).

The laser gain medium is selected to provide 1.5μm band gain for the resonator, including but not limited to Er ³⁺ doped crystal, Er ³⁺ doped glass, Er ³⁺ /Yb ³⁺ co-doped crystal and Er ³⁺ /Yb ³⁺ co-doped glass and other materials.

Saturable absorbers are selected from materials with nonlinear saturable absorption for 1.5μm wavelength lasers, including but not limited to Co ²⁺ : MgAl ₂ O ₄ , Cr ²⁺ : ZnS, semiconductor saturable absorber mirror materials, carbon nanotube materials, Two-dimensional layered materials or quantum dot materials.

Specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

Example 1

Utilize the 1.5 μm band chip-level semiconductor/solid vertically integrated passive Q-switched laser provided by Embodiment 1 of the present invention to realize Er,Yb:YAB-Co ²⁺ :MgAl ₂ O ₄ crystal-configured chip-level semiconductor/solid vertically integrated passive Q-modulated pulse output.

As shown in FIGS. 1-4 , a passively Q-switched laser includes a pump source 1 , a laser gain medium 2 and a saturable absorber 3 .

The pump source 1 is a VCSEL with a bottom emission structure, and the wavelength of the pump light 6 emitted by the VCSEL is 976nm.

VCSEL includes a substrate 105, microlenses 103 and N-type contact layer 107 are prepared at the bottom of the substrate 105, and an N-type DBR layer, active layer 104, P-type DBR layer and P-type contact layer are sequentially prepared on the top of the substrate 105 106. The substrate 105 provides a transmission distance for the pump light and provides heat dissipation. The microlens 103 focuses the pump light. The active layer 104 adopts an InGaAlAs/AlGaAs strained quantum well structure to provide gain for the VCSEL. The P-type contact layer 106 and the N-type contact layer 107 provide current injection for the VCSEL. The P-type DBR layer is used as the first reflective layer 101 , and has a high reflectivity (reflectivity R>99%) for the 976 nm pump light 6 . The N-type DBR layer is used as the second reflective layer 102 , and has a partial reflectivity (70%<reflectivity R<98%) for the 976 nm pump light 6 .

The pump source 1 shown in Figure 2 is a VCSEL with a bottom emission structure. When the pump source 1 adopts a VCSEL with a top emission structure, the N-type DBR layer is used as the first reflection layer 101, and the P-type DBR layer is used as the second reflection layer. Layer 102.

Whether it is a VCSEL with a bottom-emitting structure or a VCSEL with a top-emitting structure, the positions of the P-type DBR layer and the N-type DBR layer can be interchanged.

The laser gain medium 2 is made of Er,Yb:YAB crystal, the absorption spectrum of Er:Yb:YAB crystal can be well matched with the pump light 6 at 976 nm (as shown in Figure 5), providing a 1.5 μm The resonance gain of the resonant light 7. Er:Yb:YAB crystal has a shorter upper energy level lifetime than Er:Yb:phosphate glass, and it is easy to realize pulse output with higher repetition rate.

The surface of the laser gain medium 2 facing the pump source 1 is coated with a third reflective layer 201. The third reflective layer 201 has a high transmittance (reflectivity R<1%) for the pump light 6 of 976 nm, and for the pump light 6 of 1.34 μm Resonant light 7 exhibits high reflectivity (R>98%).

A fourth reflective layer 202 is coated on the surface of the laser gain medium 2 facing the saturable absorber 3, and the fourth reflective layer 202 has a high reflectivity (reflectivity R > 98%) for the pump light 6 of 976 nm and for the 1.5 μm The resonant light 7 has a high transmittance (reflectivity R<1%).

The first reflective layer 101, the second reflective layer 102 and the fourth reflective layer 202 form a linear three-mirror coupling cavity 4 for the pump structure, and the linear three-mirror coupling cavity 4 is used for pumping the laser gain medium 2, which is a resonant cavity 5 Provides oscillation gain.

The gain and loss of the pump source 1 can be balanced by reasonably configuring the reflectivity of the second reflective layer 102 .

The second reflective layer 102 and the fourth reflective layer 202 form a Fabry–Pérot interference cavity, which can improve the absorption effect of the laser gain medium 2 on the pumping light 6 .

The saturable absorber 3 is made of Co ²⁺ :MgAl ₂ O ₄ crystal.

A fifth reflective layer 301 is coated on the surface of the saturable absorber 3 facing the laser gain medium 2 , and the fifth reflective layer 301 has a low reflectivity (reflectivity R<1%) for the resonant light 7 of 1.5 μm.

The sixth reflective layer 302 is coated on the surface of the saturable absorber 3 facing away from the laser gain medium 2 (that is, the surface facing the light outlet), and the sixth reflective layer 302 has a partial reflectivity (50%<reflection) for the resonant light 7 of 1.5 μm Rate R<98%).

The third reflective layer 201 and the sixth reflective layer 302 form the resonant cavity 5 of the passively Q-switched laser, provide resonance feedback for the passively Q-switched laser, and emit 1.5 μm pulsed laser light.

The Er, Yb:YAB crystal provides the oscillation gain for the resonant cavity 5, and after the Co ²⁺ :MgAl ₂ O ₄ crystal modulates the intracavity loss of the resonant cavity 5, the passive Q-switched pulse laser output with an output wavelength of 1.5 μm is realized (as shown in Fig. 6).

The 1.5 μm band chip-level semiconductor/solid vertically integrated passive Q-switched laser in Embodiment 1 of the present invention can be arranged in multiples to form a laser array, such as a one-dimensional array shown in FIG. 7 and a two-dimensional array shown in FIG. 8 .

Example 2

Using the 1.5 μm band chip-level semiconductor/solid vertically integrated passive Q-switched laser provided by Embodiment 2 of the present invention, chip-level semiconductor/solid vertical integration of Er:Yb:phosphate glass-Co ²⁺ :MgAl ₂ O ₄ crystal configuration is realized Passive Q-switched pulse output.

The difference between embodiment 2 and embodiment 1 is that the Er as the laser gain medium, Yb: YAB crystal is replaced by Er: Yb: phosphate glass, Er: Yb: phosphate glass has longer upper energy level lifetime, has more Strong energy storage capacity, easy to achieve higher energy pulse laser output. However, its thermal conductivity and damage threshold are low, and it is generally only used for low repetition rate pulsed laser output.

It should be understood that steps may be reordered, added or deleted using the various forms of flow shown above. For example, the steps described in the disclosure of the present invention may be executed in parallel, sequentially, or in a different order, as long as the desired result of the technical solution disclosed in the present invention can be achieved, no limitation is imposed herein.

The above specific implementation methods do not constitute a limitation to the protection scope of the present invention. It should be apparent to those skilled in the art that various modifications, combinations, sub-combinations and substitutions may be made depending on design requirements and other factors. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (5)

1. A1.5 μm wave band chip-level semiconductor/solid vertical integrated passive Q-switched laser is characterized by comprising a pumping source, a laser gain medium and a saturable absorber which are vertically integrated in sequence by adopting a wafer bonding method; wherein,,

the pumping source adopts a vertical cavity surface emitting laser, the emission spectrum of the pumping source is matched with the absorption spectrum of the laser gain medium, a micro lens is prepared on the surface of the vertical cavity surface emitting laser, and pumping light emitted by the vertical cavity surface emitting laser enters the laser gain medium after being focused by the micro lens; taking one DBR layer of the vertical cavity surface emitting laser as a first reflecting layer, wherein the reflectivity of the first reflecting layer to the pump light is more than 99 percent, and taking the other DBR layer of the vertical cavity surface emitting laser as a second reflecting layer, wherein the reflectivity of the second reflecting layer to the pump light is 70-98 percent;

the laser gain medium is made of a material for gain of 1.5 mu m resonance light; the surface of the laser gain medium facing the vertical cavity surface emitting laser is plated with a third reflection layer, the reflectivity of the third reflection layer to pump light is less than 1 percent, and the reflectivity to 1.5 mu m resonance light is more than 98 percent; a fourth reflecting layer is plated on the surface of the laser gain medium facing the saturable absorber, wherein the reflectivity of the fourth reflecting layer to the pumping light is more than 98 percent and the reflectivity to the 1.5 mu m resonance light is less than 1 percent;

the saturable absorber adopts a material which can carry out nonlinear saturated absorption on 1.5 mu m resonance light; a fifth reflecting layer is plated on the surface of the saturable absorber facing the laser gain medium, and the reflectivity of the fifth reflecting layer to 1.5 mu m resonance light is less than 1%; a sixth reflecting layer is plated on the surface of the saturable absorber, which is far away from the laser gain medium, and the reflectivity of the sixth reflecting layer to 1.5 mu m resonance light is 50% -98%;

the third reflecting layer and the sixth reflecting layer form a resonant cavity of the passive Q-switched laser, and the resonant cavity is used for lasing the laser with the wavelength of 1.5 mu m;

the first reflecting layer, the second reflecting layer and the fourth reflecting layer form a linear three-mirror coupling cavity which is used for pumping a laser gain medium and providing oscillation starting gain for the resonant cavity;

an F-P interference cavity is formed between the second reflecting layer and the fourth reflecting layer and is used for improving the absorption rate of the laser gain medium to the pump light;

the pumping light emitted by the vertical cavity surface emitting laser enters a laser gain medium after being focused by a micro lens, the pumped laser gain medium provides optical gain for a resonant cavity, the resonant light with the wavelength of 1.5 mu m is vibrated, and after the loss in the resonant cavity is modulated by a saturable absorber, the passive Q-switched pulse laser output with the wavelength of 1.5 mu m is realized.

2. The 1.5 μm band chip-scale semiconductor/solid vertical integrated passive Q-switched laser of claim 1, wherein the laser gain medium is Er ³⁺ Doped crystalline material, er ³⁺ Doped glass material and Er ³⁺ /Yb ³⁺ Co-doped crystalline material or Er ³⁺ /Yb ³⁺ Co-doping glass materials.

3. The 1.5 μm band chip-scale semiconductor/solid vertical integrated passive Q-switched laser of claim 1, wherein the saturable absorber employs Co ²⁺ :MgAl ₂ O ₄ 、Cr ²⁺ ZnS, a semiconductor saturable absorber mirror material, a carbon nanotube material, a two-dimensional layered material or a quantum dot material.

4. The 1.5 μm band chip-scale semiconductor/solid vertical integrated passive Q-switched laser of claim 1, where the pump light has a wavelength of 976nm.

5. The 1.5 μm band chip-scale semiconductor/solid vertical integrated passive Q-switched laser of claim 1, wherein the vertical cavity surface emitting laser is a bottom emitting structure or a top emitting structure, and the microlenses are fabricated at the light outlets of the vertical cavity surface emitting lasers of the bottom emitting structure or the top emitting structure by thermal reflow, magnetron sputtering, PECVD deposition, focused ion beam etching, diffusion-limiting wet or chemical etching.