CN112366517B

CN112366517B - Tuning laser chip

Info

Publication number: CN112366517B
Application number: CN202011250258.9A
Authority: CN
Inventors: 孙文惠; 徐长达; 班德超; 陈伟; 祝宁华
Original assignee: Institute of Semiconductors of CAS
Current assignee: Institute of Semiconductors of CAS
Priority date: 2020-11-10
Filing date: 2020-11-10
Publication date: 2022-04-22
Anticipated expiration: 2040-11-10
Also published as: CN112366517A

Abstract

A tuned laser chip, comprising: the micro-ring resonant cavity comprises a backward grating area (1), a first gain area (2), a micro-ring resonant cavity (c) and a forward grating area (5); the micro-ring resonant cavity (c) comprises a second gain region (3), a first multimode interference waveguide (6), a phase modulation region (4) and a second multimode interference waveguide (7) which are sequentially connected in an annular manner; the backward grating region (1) is connected to the first gain region (2), the first gain region (2) is connected to the first multimode interference waveguide (6), the forward grating region (5) is connected to the second multimode interference waveguide (7); the backward grating region (1) and the forward grating region (5) form a Bragg reflection resonant cavity, and the second gain region (3) and the phase modulation region (4) form a gain resonant cavity. The laser chip can realize fine tuning and wide-range tuning of an L-band spectrum and avoid mode hopping.

Description

Tuning laser chip

Technical Field

The present disclosure relates to the field of optoelectronic chips, and more particularly, to a tunable laser chip.

Background

The semiconductor laser has high coherence, low frequency noise, high frequency stability and wide wavelength tuning potential, and thus becomes a core device in the fields of ultrahigh-speed optical communication, long-distance spatial laser communication, ultrahigh-resolution laser radar, optical sensing and the like. In 100Gbps and ultra-100 Gbps high-speed optical communication systems, the rapid increase of data load promotes the use of high-order quadrature amplitude modulation schemes such as 16-QAM, 64-QAM and the like, the tolerance to phase noise is low, and the laser is required to have tunability of a full C wave band and even a full L wave band.

From practical application, a Wavelength Division Multiplexing (WDM) transmission system needs to consider the limitation of a tunable light source while considering the increase of bandwidth and capacity, and how to realize a wide-range Wavelength scanning light source satisfying an L-band is a difficult problem troubling researchers in recent years, and the size of an optical transmission module given to a communication system is limited, and a single module faces a huge challenge in realizing wide-range tuning and fast switching.

Disclosure of Invention

Technical problem to be solved

In view of the above-mentioned problems, the present disclosure provides a tunable laser chip, which at least partially solves one of the above-mentioned problems.

(II) technical scheme

An aspect of the disclosed embodiments provides a tuned laser chip, including: the device comprises a backward grating area 1, a first gain area 2, a micro-ring resonant cavity c and a forward grating area 5; the micro-ring resonant cavity c comprises a second gain region 3, a first multimode interference waveguide 6, a phase modulation region 4 and a second multimode interference waveguide 7 which are sequentially connected in an annular manner; the backward grating region 1 is connected to the first gain region 2, the first gain region 2 is connected to the first multimode interference waveguide 6, and the forward grating region 5 is connected to the second multimode interference waveguide 7; wherein, backward grating area 1 and forward grating area 5 constitute Bragg reflection resonant cavity, and second gain area 3 and phase modulation area 4 constitute gain resonant cavity.

According to the embodiment of the present disclosure, the FSR of the micro-ring resonator c is greater than or equal to one half of the stop band width of the bragg-reflective resonator grating.

According to the embodiment of the present disclosure, the backward grating region 1 is a bragg grating etching waveguide layer, and the light incident end thereof is plated with a reflective film.

According to the embodiment of the present disclosure, the forward grating region 5 is a bragg grating etched waveguide layer, and the light emitting end thereof is plated with an anti-reflection film.

According to the embodiment of the present disclosure, there is a preset period difference between the backward grating region 1 and the forward grating region 5.

According to the embodiment of the present disclosure, the first gain region 2 has a gain spectrum range of the L-band.

According to an embodiment of the disclosure, wherein the gain spectrum wavelength range comprises 1570nm-1610 nm.

According to the embodiment of the present disclosure, the second gain region 3 has a gain spectrum range of the L-band.

According to the embodiment of the present disclosure, the phase modulation region 4 is a passive waveguide structure.

(III) advantageous effects

The tuning laser chip provided by the disclosure has the beneficial effects that:

because the tuning laser chip is composed of a micro-ring resonant cavity structure and a double-DBR (Bragg reflection) grating structure, the vernier effect of the double-DBR grating structure can be utilized for wavelength selection, meanwhile, the free carrier dispersion effect of the micro-ring resonant cavity structure is utilized, the current is controlled to change the refractive index of the waveguide, so that the transmission spectrum of the micro-ring resonant cavity deviates from a longitudinal mode, wavelength auxiliary tuning and phase fine tuning are carried out, the side mode rejection ratio is optimized, and therefore fine tuning and wide-range tuning of the L-waveband spectrum are realized, and mode hopping is avoided.

The FSR of the micro-ring resonant cavity is set to be more than or equal to one half of the width of the stop band of the Bragg reflection resonant cavity grating, so that the purposes of optimizing the side mode suppression ratio and tuning the L-waveband in a wide range can be further achieved.

Drawings

FIG. 1 schematically illustrates a tuned laser chip architecture provided by an embodiment of the present invention;

fig. 2 schematically illustrates a tuning spectrum of a tuned laser chip provided by an embodiment of the disclosure.

[ reference numerals ]

1-backward grating area, 2-first gain area, c-micro ring resonant cavity, 3-second gain area, 4-phase modulation area, 5-forward grating area, 6-first multimode interference waveguide, and 7-second multimode interference waveguide.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is illustrative only and is not intended to limit the scope of the present disclosure. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure.

The injection current of the conventional DBR laser only passes through the passive waveguide region where the grating is located, the change of the Bragg wavelength determined by the grating along with the temperature is faster than the change of the active region lasing mode along with the temperature, and mode hopping occurs when the difference of the changes is larger than the half-pitch of the lasing mode of the DBR laser. Based on the problem, the embodiment of the disclosure provides a tuned laser chip, which is designed reasonably according to the structure and parameters of the tuned laser chip, so as to realize L-band wide-range tuning and avoid mode hopping.

Fig. 1 schematically shows a structure diagram of a tuned laser chip provided by an embodiment of the present invention.

As shown in fig. 1, the tuned laser chip may include, for example:

backward grating area 1, first gain area 2, micro-ring resonant cavity c and forward grating area 5. The micro-ring resonator c may include, for example, a second gain region 3, a first multimode interference waveguide 6, a phase modulation region 4, and a second multimode interference waveguide 7, which are sequentially connected in an annular shape, that is, the second gain region 3, the first multimode interference waveguide 6, the phase modulation region 4, and the second multimode interference waveguide 7 are connected at the head to form an annular structure. The backward grating region 1 is connected to a first gain region 2, the first gain region 2 is connected to a first multimode interference waveguide 6, and the forward grating region 5 is connected to a second multimode interference waveguide 7. The backward grating region 1 and the forward grating region 5 may form a bragg reflection resonant cavity, and the second gain region 3 and the phase modulation region 4 may form a gain resonant cavity.

In some embodiments of the present disclosure, the backward grating region 1 may be a bragg grating etched waveguide layer, the light-entering end of which may be plated with a high reflection film, the forward grating region 5 may also be a bragg grating etched waveguide layer, and the light-exiting end of which may be plated with an anti-reflection film. The forward grating region 5 may be, for example, a bragg grating region having a preset slight period difference from the backward grating region 1. The backward grating region 1 and the forward grating region 5 form a bragg reflection resonant cavity (a double grating structure) which can determine the space between cavity films.

In some embodiments of the present disclosure, the first gain region 2 may have a gain spectrum range of the L-band, which may cover 1570nm-1610nm in wavelength range. The second gain region 3 may have a gain spectrum range of the L-band, which may cover 1570nm-1610nm in wavelength. The range of the gain spectrum of the first gain region 2 and the second gain region 3 may be determined by the design of the material.

In some embodiments of the present disclosure, phase modulation region 4 may be, for example, a passive waveguide structure. The phase modulation region 4 can generate a carrier diffusion effect through electrode control, and phase tuning is realized. The gain cavity formed by the second gain region 3 and the phase modulation region 4 in the ring can be determined by the effective cavity length of the micro-ring cavity, and is used for narrowing the line width of the spectrum.

In some embodiments of the present disclosure, the FSR of the micro-ring resonator c may be set to be greater than or equal to one-half of the stop-band width of the bragg-reflective resonator grating.

The wavelength selection of the tuning laser chip is determined by a longitudinal mode matched with a resonance peak of mutual overlapping of a longitudinal mode generated by a DBR resonant cavity and a micro-ring resonant cavity. The wide-range tuning is mainly based on a DBR (distributed Bragg Reflector) tuning mechanism, the micro-ring resonant cavity structure c can perform auxiliary filtering and fine phase adjustment, the side mode rejection ratio is optimized, and the occurrence of mode hopping is effectively avoided. The mechanism principle is specifically analyzed in conjunction with fig. 2.

Specifically, as shown in fig. 2, the double DBR double grating structure uses its vernier effect for wavelength selection. The refractive index of the waveguide is changed by controlling the current through the free carrier dispersion effect, so that the transmission spectrum of the micro-ring resonant cavity deviates from a longitudinal mode, wavelength-assisted tuning and phase fine tuning are carried out, the spectrum can be finely tuned, and mode hopping is avoided. Namely, the tuning of the wavelength mainly utilizes the vernier effect of the DBR grating and the free carrier dispersion effect of the waveguide material of the micro-ring resonant cavity to realize the wide-range mode-hopping-free tuning.

Further, the FSR of the micro-ring resonator structure is set at more than half of the stop band width of the DBR double-grating, and the transmissivity reaches the maximum value at the maximum overlapping position of the longitudinal mode and the resonance peak. Through the design, the responsibility of the definite division micro-ring resonant cavity lies in fine phase adjustment and fine filtering, the DBR double-grating performs wide-range tuning, the micro-ring resonant cavity structure adopts a tuning mechanism based on free carrier dispersion effect to match with the vernier effect of the DBR double-grating to realize the wide-range tuning, and through the phase micro-tuning of the micro-ring resonant cavity, the mode jump is avoided, meanwhile, the unimpeded switching of a communication channel is realized, and the purposes of optimizing the side mode rejection ratio and the wide-range tuning are further achieved.

To sum up, the tunable laser chip provided by the embodiment of the present disclosure, through the design of the DBR double grating position and the grating period, not only meets the requirement of tuning in a wide range across the L-band, but also ensures that the grating coupling efficiency is moderate, ensures sufficient optical power output, and also skillfully avoids spatial hole burning and excessive loss. Meanwhile, the phase modulation region performance of the micro-ring resonant cavity structure and the DBR double-grating design are optimized, so that the cross-band tuning range is met while the low transmission loss is obtained. The DBR double-grating and micro-ring resonant cavity structure realizes wide-range tuning through a tuning mode combining two mechanisms, free carriers are injected into a tuning area through injection current, and the refractive index is changed due to the energy band filling effect and the free carrier absorption effect of the free carriers, so that tuning is realized.

It will be understood by those skilled in the art that while the present disclosure has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents. Accordingly, the scope of the present disclosure should not be limited to the above-described embodiments, but should be defined not only by the appended claims, but also by equivalents thereof.

The above-mentioned embodiments are intended to illustrate the objects, aspects and advantages of the present disclosure in further detail, and it should be understood that the above-mentioned embodiments are only illustrative of the present disclosure and are not intended to limit the present disclosure, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present disclosure should be included in the scope of the present disclosure.

Claims

1. A tuned laser chip, comprising:

the micro-ring resonant cavity comprises a backward grating area (1), a first gain area (2), a micro-ring resonant cavity (c) and a forward grating area (5);

the micro-ring resonant cavity (c) comprises a second gain region (3), a first multimode interference waveguide (6), a phase modulation region (4) and a second multimode interference waveguide (7) which are sequentially connected in an annular manner; the backward grating region (1) is connected to the first gain region (2), the first gain region (2) is connected to the first multimode interference waveguide (6), the forward grating region (5) is connected to the second multimode interference waveguide (7);

the backward grating region (1) and the forward grating region (5) form a Bragg reflection resonant cavity, and the second gain region (3) and the phase modulation region (4) form a gain resonant cavity;

the FSR of the micro-ring resonant cavity (c) is more than or equal to one half of the stop band width of the Bragg reflection resonant cavity grating.

2. The tuned laser chip of claim 1, wherein the backward grating region (1) is a bragg grating etched waveguide layer, and the light-incident end thereof is coated with a reflective film.

3. The tuned laser chip of claim 1, wherein the forward grating region (5) is a bragg grating etched waveguide layer, and the light exit end thereof is coated with an antireflection coating.

4. The tuned laser chip according to claim 1, wherein the backward grating region (1) and the forward grating region (5) have a preset period difference.

5. The tuned laser chip of claim 1, wherein the first gain region (2) has a gain spectral range of the L-band.

6. The tuned laser chip of claim 5, wherein the gain spectrum wavelength range comprises 1570nm-1610 nm.

7. The tuned laser chip according to claim 1, wherein the second gain region (3) has a gain spectral range of the L-band.

8. The tuned laser chip of claim 7, wherein the gain spectrum wavelength range comprises 1570nm-1610 nm.

9. The tuned laser chip according to claim 1, wherein the phase-modulating region (4) is a passive waveguide structure.