CN-121983849-A - Distributed feedback laser based on asymmetric sampling grating and manufacturing method thereof

CN121983849ACN 121983849 ACN121983849 ACN 121983849ACN-121983849-A

Abstract

The invention discloses a distributed feedback laser based on asymmetric sampling grating and a manufacturing method thereof, belonging to the technical field of laser, wherein in the grating structure of the laser, the equivalent pi phase shift is located off the center of the cavity and the duty cycle of the sampled grating, i.e., the ratio of the sampling window length to the sampling period, is less than 0.5. The invention adopts the reconstruction equivalent chirp technology, combines the asymmetric phase shift and the asymmetric coupling coefficient design, and remarkably improves the forward output power. In the laser structure, asymmetric regulation and control of photon density distribution are realized by optimizing the phase shift position and the duty ratio of the sampling grating, so that the forward output power is improved on the premise of keeping the stability of a single longitudinal mode. The invention adopts micron-scale photoetching technology to prepare the sampling structure, reduces the dependence on high-precision electron beam photoetching, and improves the manufacturing tolerance and the cost efficiency. Experimental results show that the laser is stable in spectrum when working in the C wave band, and the side mode suppression ratio is higher than 50 dB.

Inventors

LI SIYING
WANG ZHUOYING
CHEN XIANGFEI
SUN ZHENXING

Assignees

南京大学

Dates

Publication Date: 20260505
Application Date: 20260121

Claims (8)

1. The utility model provides a distributed feedback laser based on asymmetric sampling grating which characterized in that: in the grating structure of the laser, the equivalent pi phase shift position deviates from the center of the cavity, and the duty ratio of the sampling grating is less than 0.5.
2. The asymmetric sampled grating-based distributed feedback laser of claim 1, wherein: The ratio of the position of the equivalent pi phase shift to the cavity length is a relative position parameter, the value range of the relative position parameter is 0.35-0.65, and the relative position parameter is preferably 0.55.
3. The asymmetric sampled grating-based distributed feedback laser of claim 1, wherein: the value range of the duty ratio is 0.30-0.45, and the preferable duty ratio is 0.40.
4. The asymmetric sampled grating-based distributed feedback laser of claim 1, wherein: the laser adopts a reconstruction equivalent chirp technology to prepare a sampling grating, and an equivalent asymmetric structure is realized through a micron-scale photoetching technology.
5. The asymmetric sampled grating-based distributed feedback laser of claim 1, wherein: The laser is of a ridge waveguide structure and comprises a substrate, a buffer layer, a lower limiting layer, a multi-quantum well gain layer, an upper limiting layer, a grating layer, a buried layer, a corrosion barrier layer, a waveguide layer and a contact layer from bottom to top.
6. The asymmetric sampled grating-based distributed feedback laser of claim 5, wherein: the grating layer is made of p-type InGaAsP material, and the working wavelength is located in the center of the gain bandwidth.
7. The asymmetric sampled grating-based distributed feedback laser of claim 5, wherein: The substrate is made of n-type InP material; The buffer layer is made of n-type InP material; The lower limiting layer comprises an n-type limiting layer and an undoped limiting layer from bottom to top; The multi-quantum well gain layer is made of InAlGaAs material; the buried layer is made of p-type InP material; the contact layer is a p-type contact layer.
8. The method for manufacturing the asymmetric sampling grating-based distributed feedback laser according to any one of claims 5 to 7, wherein the method comprises the following steps: Sequentially growing the buffer layer and the lower limiting layer on the substrate through metal organic compound vapor deposition, growing the multiple quantum well gain layer on the lower limiting layer, growing the upper limiting layer on the multiple quantum well gain layer, depositing a grating above the upper limiting layer as a grating layer, growing the buried layer above the grating layer, and sequentially growing the corrosion barrier layer, the waveguide layer and the contact layer on the buried layer.

Description

Distributed feedback laser based on asymmetric sampling grating and manufacturing method thereof Technical Field The invention belongs to the technical field of lasers, and relates to a laser, in particular to a distributed feedback laser based on an asymmetric sampling grating and a manufacturing method thereof. Background The distributed feedback laser is widely applied to the fields of optical communication, laser radar, microwave photonics and the like due to the advantages of single longitudinal mode stability, low threshold value, narrow linewidth and the like. Conventional distributed feedback lasers typically employ a centrally symmetric lambda/4 phase shift and a uniform grating design, resulting in symmetric front-to-back output power, with only about 50% of the forward available power. In addition, photon density concentration at high currents can exacerbate carrier non-uniformity, affecting single mode stability. To improve output power and stability, researchers have proposed asymmetric phase shift and asymmetric coupling coefficient techniques. However, the fabrication of these non-uniform grating structures relies on high precision electron beam lithography, which has problems of splice errors, long fabrication cycles, and high costs. The Reconstruction Equivalent Chirp (REC) technology converts a nanoscale structure into a structure which can be realized by micron-scale photoetching through a sampling grating design, and the manufacturing precision and tolerance are obviously improved. However, no system combines asymmetric phase shift, asymmetric coupling coefficient and reconstruction equivalent chirp technology to realize the mature scheme of the high-power and high-stability distributed feedback laser. Disclosure of Invention Aiming at the technical problem that the output power, single-mode stability and manufacturing cost of the existing distributed feedback laser are difficult to consider, the invention provides the distributed feedback laser based on the asymmetric sampling grating and the manufacturing method thereof, which realize remarkable improvement of the output power through structural innovation and process optimization, ensure excellent single-longitudinal mode characteristics and greatly reduce manufacturing complexity and cost. In order to achieve the above purpose, the present invention adopts the following technical scheme: In a first aspect, the present invention provides a distributed feedback laser based on an asymmetric sampling grating, in which the position of the equivalent pi phase shift is offset from the cavity center in the grating structure of the laser, and the duty cycle of the sampling grating, i.e. the ratio of the sampling window length to the sampling period, is less than 0.5. The invention realizes the remarkable improvement of forward output power through the design of asymmetric phase shift and asymmetric coupling coefficient. In order to optimize the technical scheme, the specific measures adopted further comprise: Further, the ratio of the position of the equivalent pi phase shift to the cavity length is a relative position parameter, the value range of the relative position parameter is 0.35-0.65, and preferably, the relative position parameter is 0.55, namely, the position of the equivalent pi phase shift is offset from the center of the cavity to the front end output surface. The asymmetric phase shift design of the invention can effectively break the symmetrical distribution of photon density in the resonant cavity, and promote the optical energy to be more concentrated at the front end, thereby directly improving the forward output power. Further, the value range of the duty ratio is 0.30-0.45, and preferably, the duty ratio is 0.40. The asymmetric coupling coefficient is introduced by regulating and controlling the duty ratio of the sampling grating, and the asymmetric distribution of the coupling coefficient not only cooperates with the phase shift design to enhance the power output of the front end, but also is beneficial to inhibiting the space hole burning effect caused by the uneven distribution of carriers under high injection current, thereby improving the single longitudinal mode stability of the laser. Furthermore, the laser adopts a reconstruction equivalent chirp technology to prepare the sampling grating, and realizes an equivalent asymmetric structure through a micron-scale photoetching technology, thereby avoiding the splicing error of electron beam photoetching. Specifically, the asymmetric nanoscale grating characteristic is not directly realized by a high-precision electron beam lithography technology, but is innovatively realized by adopting a reconstruction equivalent chirp technology and combining holographic exposure with a micron-scale contact lithography technology. The technical path widens the manufacturing requirement of critical dimensions from nano dimensions to micro dimensions, remarkably reduces the dependence