CN212991573U

CN212991573U - Distributed feedback laser of phase shift grating

Info

Publication number: CN212991573U
Application number: CN202021702716.3U
Authority: CN
Inventors: 孙维忠; 蔡文必
Original assignee: Xiamen Sanan Integrated Circuit Co Ltd
Current assignee: Quanzhou San'an Optical Communication Technology Co ltd
Priority date: 2020-08-13
Filing date: 2020-08-13
Publication date: 2021-04-16
Anticipated expiration: 2030-08-13

Abstract

The utility model discloses a distributed feedback laser of phase shift grating, which comprises an active area, a grating layer and a waveguide layer which are arranged from bottom to top in sequence; the grating layer comprises three sections of first gratings and two sections of second gratings, the first gratings have standard periods, and the periods of the second gratings are different from the standard periods; the first grating and the second grating are arranged alternately along the cavity length direction of the laser, wherein the two sections of the second gratings are respectively positioned at 1/3 and 2/3 of the cavity length of the laser, and the reflected phase of the second grating is 1/8 wavelength to serve as a phase shift region, so that the single longitudinal mode work of the laser is realized, the photon concentration of the phase shift region is effectively reduced, the photon uniformity of the whole laser is better, and the space burning empty effect of the laser is inhibited.

Description

Distributed feedback laser of phase shift grating

Technical Field

The utility model relates to a technical field of laser instrument especially relates to a distributed feedback laser instrument of phase shift grating.

Background

Currently, the grating of Distributed Feedback (DFB) lasers typically employs a uniform grating. Due to errors in cleavage, the HR end face reflection phase of the DFB laser has randomness, and the problem that the single-mode yield of the DFB laser with the common uniform grating is low is caused. The single-mode yield is generally 20-40%. To solve this problem, quarter-wave phase shift (QWPS) grating DFB lasers have been invented. The QWPS DFB laser introduces quarter-wavelength phase shift in the middle of the grating, and due to the introduction of the quarter-wavelength phase shift, dual-mode degeneracy in a common uniform grating DFB is broken, so that the laser outputs in a single longitudinal mode. Theoretically, the single mode yield of a QWPS DFB laser is 100%. However, due to the introduction of the phase shift region, the photon concentration in the phase shift region in the laser resonant cavity is very high, which causes the QWPS DFB laser to have a serious space burning-out effect, and particularly, the space burning-out phenomenon is more obvious when a large current is injected. Severe spatial burn-in effects can affect the DC characteristics of the laser, for example, causing multimode operation of the laser. Particularly, for a DFB laser applied to high-speed modulation, the cavity length is short, the modulated dc bias is large, and the laser is prone to multimode.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to overcome the not enough of prior art existence, provide a distributed feedback laser of phase shift grating.

In order to realize the above purpose, the technical scheme of the utility model is that:

a distributed feedback laser of phase shift grating comprises an active region, a grating layer and a waveguide layer which are arranged from bottom to top in sequence; the grating layer comprises three sections of first gratings and two sections of second gratings, the first gratings have standard periods, and the periods of the second gratings are different from the standard periods; the first grating and the second grating are alternately arranged along the cavity length direction of the laser, wherein the two sections of the second grating are respectively positioned at 1/3 and 2/3 of the cavity length of the laser, and the phase of the reflection of the second grating is 1/8 wavelengths.

Optionally, the length of each section of the second grating is 5-20 μm.

Optionally, the period of the second grating is smaller than the standard period.

Optionally, the difference between the period of the second grating and the standard period is 0.1nm to 5 nm.

Optionally, the semiconductor device further includes a substrate disposed below the active region, a first electrode disposed below the substrate, and a second electrode disposed above the waveguide layer.

Optionally, the substrate is made of N-InP, the active region includes AlGaInAs multiple quantum wells, the grating layer is made of p-InGaAsP, and the waveguide layer is made of InP.

Optionally, the wavelength of the laser is 1310nm, the cavity length is 250 μm, the standard period of the first grating is 202.1nm, the period of the second grating is 201nm, and the length of each segment of the second grating is 15 μm.

The utility model has the advantages that:

two second gratings with different standard periods are used and placed at 1/3 and 2/3 of the laser cavity as phase shifting regions. The single longitudinal mode operation of the laser is realized. The lengths of the two sections of second gratings reach the magnitude of mum, and compared with the traditional phase shift region with the magnitude of nm, the lengths of the two sections of second gratings are greatly increased, so that the photon concentration of the phase shift region can be effectively reduced, the photon uniformity of the whole laser is better, and the space burning-out effect of the laser is inhibited. The single-mode stability of the laser under the condition of high-current injection can be improved, and the DC performance of the laser is improved.

Drawings

FIG. 1 is a schematic diagram of a distributed feedback laser with a phase-shifted grating according to an embodiment;

fig. 2 is a schematic diagram of the structure of the grating layer in fig. 1.

Detailed Description

The invention is further explained below with reference to the drawings and the specific embodiments. The utility model discloses an each drawing only is the schematic in order to understand more easily the utility model discloses, its specific proportion can be adjusted according to the design demand. The relative positions of elements in the figures described herein are understood by those skilled in the art to refer to relative positions of elements, and thus all elements may be reversed to represent the same, all falling within the scope of the disclosure.

Referring to fig. 1, the distributed feedback laser of the phase shift grating of the embodiment includes a first electrode 1, a substrate 2, an active region 3, a grating layer 4, a waveguide layer 5, and a second electrode 6, which are sequentially arranged from bottom to top. With reference to fig. 1 and fig. 2, the grating layer 4 includes three segments of first gratings 41 and two segments of second gratings 42, the first gratings 41 have a standard period, and the period of the second gratings 42 is different from the standard period; the first gratings 41 and the second gratings 42 are arranged alternately along the cavity length of the laser, wherein two segments of the second gratings 42 are respectively positioned at 1/3 and 2/3 of the cavity length of the laser, and the phase of the reflection of the second gratings 42 is 1/8 wavelengths. The standard period mentioned here means a period of a uniform grating set in correspondence with a target wavelength for realizing the laser. 1/3 and 2/3 are used to indicate that the starting positions of the two segments of the second grating 42 are at the 1/3 and 2/3 positions of the laser cavity length, respectively. The two sections of the second grating 42 replace the traditional phase shift region in the phase of the light reflection, and the period and the length of the second grating are designed to ensure that the phase of the reflection is exactly 1/8 wavelengths (namely pi/2), so that the equivalent of introducing one-eighth wavelength phase shift regions at 1/3 and 2/3 of the cavity length of the laser is realized, and the single longitudinal mode operation of the laser is realized.

The period of the second grating 42 is smaller than the standard period. The difference between the period of the second grating and the standard period is 0.1 nm-5 nm. The length of each section of the second grating 42 is 5-20 μm. Compared with the traditional phase shift region (the length is about 50 nm), the length of the phase shift region is increased by 2 orders of magnitude, so that photons originally concentrated on 50nm can be distributed in 5-20 mu m, the photon concentration of the phase shift region is reduced, the photon uniformity of the whole laser is better, and the suppression of the longitudinal space burning-in effect in the laser is facilitated.

Taking a 1310nm laser structure as an example, the material of the substrate 2 is N-InP, the active region 3 is an AlGaInAs multiple quantum well, the material of the grating layer 4 is P-InGaAsP, the material of the waveguide layer 5 is InP, the first electrode 1 is an N electrode, and the second electrode 6 is a P electrode. The cavity length of the laser is 250 μm, the standard period of the first grating 41 is 202.1nm, the period of the second grating 42 is 201nm, and the length of each section of the second grating 42 is 15 μm. Assuming that the laser equivalent refractive index neff is 3.24, the perspective phase of the second grating 42 to the light is exactly pi/2, i.e. an eighth wavelength phase shift. And both ends of the laser are plated with anti-reflection (AR) films. Through the structure, the single-mode operation of the laser is ensured, and meanwhile, the longitudinal space burning-out effect of the laser is inhibited. The single-mode operation of the laser is more stable under large current, and the DC performance is better.

The above embodiments are only used to further illustrate the distributed feedback laser of the phase shift grating of the present invention, but the present invention is not limited to the embodiments, and any simple modification, equivalent change and modification made by the technical entity of the present invention to the above embodiments all fall into the protection scope of the technical solution of the present invention.

Claims

1. A phase shifted grating distributed feedback laser, comprising: the grating waveguide structure comprises an active region, a grating layer and a waveguide layer which are arranged from bottom to top in sequence; the grating layer comprises three sections of first gratings and two sections of second gratings, the first gratings have standard periods, and the periods of the second gratings are different from the standard periods; the first grating and the second grating are alternately arranged along the cavity length direction of the laser, wherein the two sections of the second grating are respectively positioned at 1/3 and 2/3 of the cavity length of the laser, and the phase of the reflection of the second grating is 1/8 wavelengths.

2. A distributed feedback laser for a phase shifted grating as claimed in claim 1, wherein: the length of each section of the second grating is 5-20 mu m.

3. A distributed feedback laser for a phase shifted grating as claimed in claim 1, wherein: the period of the second grating is smaller than the standard period.

4. A distributed feedback laser for a phase shifted grating as claimed in claim 1, wherein: the difference between the period of the second grating and the standard period is 0.1 nm-5 nm.

5. A distributed feedback laser for a phase shifted grating as claimed in claim 1, wherein: the semiconductor device further comprises a substrate arranged below the active region, a first electrode arranged below the substrate and a second electrode arranged above the waveguide layer.

6. The phase-shifted grating distributed feedback laser of claim 5, wherein: the material of the substrate is N-InP, the active region comprises an AlGaInAs multi-quantum well, the material of the grating layer is p-InGaAsP, and the material of the waveguide layer is InP.

7. A distributed feedback laser for a phase shifted grating as claimed in claim 1, wherein: the wavelength of the laser is 1310nm, the cavity length is 250 microns, the standard period of the first grating is 202.1nm, the period of the second grating is 201nm, and the length of each section of the second grating is 15 microns.