SU1730604A1 - Waveguide reflective cell - Google Patents

Abstract

The invention relates to integrated optics and can be used in the structures of semiconductor injection lasers, spectral filters, mode converters. The purpose of the invention is to simplify use in devices made according to planar technology and to increase the reflection coefficient. The Brechlow reflector corrugation is made on the side surfaces of the comb waveguide, while the upper surface can be used to apply planar electrode or waveguide structures. The reflection coefficient increases, since at a given depth of modulation of the thickness, the corrugations can easily be made symmetrical on opposite sides of the comb waveguide. 2 Il.

Description

The invention is intended for use in integrated optics and integrated optoelectronics in the creation of distributed Bragg reflectors (DBRs), narrowband filters, deflectors and elements of POC and RBR lasers.

Among the elements of integrated optics and integrated optoelectronics, reflective elements (DFB and DBR) are known, consisting of optical planar or strip waveguides containing a corrugated portion of the surface of the interface between the waveguide media. Such POC and PBR elements are performed using holography by exposing the photoresist layer to an interference pattern with the required corrugation period and subsequent appearance and etching.

These elements have the following disadvantages:

difficulties of using integrated technology in the manufacture of integral

optical circuits, since the manufacture of POC and OBR elements requires the use of holographic methods that violate the unified technology for the formation of integrated circuits;

the shape of the corrugation profile is different from the sinusoidal method by the holographic method of manufacturing RBT and DFB elements, which creates scattering losses in these elements, and in lasers leads to an increase in the generation threshold;

the difficulty of obtaining reflection coefficients close to unity at small waveguide lengths (on the order of 10 microns) characteristic of integrated optoelectronics.

In practice, used injection semiconductor lasers with POC and SBR reflectance coefficients for lengths of the corrugated section of 10 µm are significantly less than 0.1 due to the small depth of the corrugation. At great depths of the corrugation, its profile existed

with

Xi so about about u

The difference in rusts is sinusoidal, which leads to a significant loss of laser power and requires an increase in the pump current.

The purpose of the invention is the possibility of simplifying the use of plenary integrated optical technology in the creation of POC- and RBR-elements, as well as obtaining high reflection coefficients (close to unity) in the POC- and RBR-elements.

The goal is achieved by the fact that instead of a corrugation with a small depth (amplitude) on the interface surface of the comb strip waveguide (Fig.1), a corrugation is created on the sides of the comb waveguide (Fig.2) using a mask.

Figure 1 and 2 shows the waveguide reflective elements.

The waveguide reflective element contains a comb-shaped strip waveguide 1 (Fig. 2), which is a rectangular section with dimensions of 2S x 2d of a material with a refractive index greater than the substrate’s refractive index and the refractive indices above and to the side of him (pa and iv). The side surfaces 2 of the comb-shaped strip waveguide are corrugated with a corrugation period L defined by the expression I

L (1)

2 n 1eff

where n 1Ef is the effective refractive index of a strip waveguide, and I is the radiation wavelength.

The action of DBR and DFB is based on the use of the Bragg reflection effect, when only radiation with a wavelength satisfying condition (1) is reflected and in phase. Compared to the prototype, the reflection coefficient of Bragg structures with corrugated side surfaces is approximately an order of magnitude higher due to the large amplitude of the corrugation.

The light reflection coefficient g obtained in this case can be estimated, for example, using the formula for a symmetric waveguide with a symmetric in-phase corrugation. , l l, o l,

IP 2, e (i-nl) KoCosVflcf

Г ™ ab4№ / Wo) 2

where P and AR are the incident and reflected powers;

t, pz are the refractive indices of the waveguide layer and waveguide layers of the surrounding media;

 - the wave number of the incident and reflected waveguide modes;

d is half the thickness of the waveguide layer;

Xo ul-ftl

.

I - wavelength in vacuum;

a is the amplitude of the corrugation;

L is the length of the corrugated area.

This formula can be applied to estimate a comb-shaped strip waveguide with a corrugation on the side walls. For simplicity, however, it is assumed that the thickness of wave 0

five

0

0

five

water layer 2d is equal to the width of the comb-shaped strip waveguide 2S, and n / P2 is the refractive index of the side media of the comb-shaped strip waveguide. Reflection coefficient 0 for a comb-shaped waveguide with parameters:

T 3.6 (Ga As); P2 3,4 (Ga Al As); n 3.4 (Ga Al As); I am 0.6 microns; # 0 0.84 K0; y0 0.83 K0; d 0.5 microns; L 10 microns; d 5 o, 2 µm, and the corrugation on the side walls is 80%. As d increases, the reflection coefficient g approaches 100%.

In addition, the proposed structure allows to simplify the technological process during their production. This is achieved by the fact that the manufacturing process of the comb-shaped strip waveguide and the Bragg structure, as well as other elements of the optical scheme, is combined, i.e. produced by a single technological act, rather than in stages (as in the prototype).

For the practical implementation of these waveguide Bragg structures, photo-, electron-, ion-or-x-ray lithography should be used to create injection heterostructures on gallium arsenide and obtain the configuration of the layers shown in Fig.2. 5 The design and method for the specific implementation of the proposed waveguide reflective elements has a significant novelty.

The proposed invention can be implemented in the electronics industry.

Claims (1)

Invention Formula A waveguide reflective element comprising a comb-shaped strip waveguide with a means of spatial modulation of a constant propagation of a waveguide mode, made in the form of a corrugation on the surface of a waveguide, characterized in that, in order to simplify use in devices made According to the planar technology and the enhancement of the lateral surfaces of the comb wave reflection coefficient, the corrugation is made on water. Fig 1. , .III ./Г Л t Г4 О K C - s - 1 b And g d g I-1 yr -U- i -4-A pp View from above section YES P., Y p & I L L A / vi L7 v. V / h- / -j u Mi h / vwf. -i Gb