Method of preparation of quantum cascading laser buried double-cycle grating with double holographic exposure

Abstract

The invention discloses a method of the preparation of a quantum cascading laser buried double-cycle grating with double holographic exposure. The method includes the following steps: step 1, subjecting a lower waveguide layer, a lower light limit layer, a laser active area and an upper light limit layer to epitaxial growth on a semiconductor substrate to obtain quantum cascading laser epitaxy chips with light limit layer structures; step 2, washing the epitaxy chips; step 3, evenly coating the surfaces of the epitaxy chips with photoresist; step 4, using the method of holographic exposure, subjecting the photoresist to two-time exposure which is of a corresponding dose and different in table included angle; step 5, developing and shaping the epitaxy chips after exposure treatment to obtain photoresist grating graphics; step 6, subjecting the epitaxy chips to hardening treatment, and then using a plasma resist remover to remove the residual photoresist; step 7, taking the photoresist grating graphics as masks to corrode the epitaxy chips, and transferring the grating graphics to the light limit layers; and step 8, using organic solvents to clean the photoresist grating graphics to prepare the double-cycle grating, and the preparation is completed.

Description

technical field [0001] The invention relates to the technical field of semiconductor optoelectronics, in particular to a method for making a double-period grating buried in a quantum cascade laser. Background technique [0002] There are usually two methods for fabricating small-period (less than 1 μM) gratings in semiconductor optoelectronic devices: holographic exposure and electron beam exposure. [0003] The holographic exposure method uses two beams of coherent light with the same wavelength to be incident on the surface of the substrate at a certain angle to form light and dark interference fringes, and these interference patterns are recorded through the photoresist coated on the surface, and can be formed after development. A photoresist grating mask with a uniform period, and then the grating pattern is transferred to the substrate surface by an etching process (wet or dry etching). The holographic exposure system has simple equipment, low cost, and the exposure cy...

AI Technical Summary

Problems solved by technology

However, the cavity length of the quantum cascade laser is long (about 2mm), the coupling strength (the product of the coupling coefficient and the cavity length) is too large, and the laser works in an over-coupling state, which is not conducive to high-power output

[0007] Double-period gratings are used in the buried grating structure of quantum cascade lasers. It shows the grating coupling coefficient and the duty cycle of the large-period grating (Λ s / Λ L / 2 ) is directly proportional to, an excessively large duty cycle can achieve a lower coupling coefficient, but it will also shorten the interval of the comb reflection spectrum introduced by the large-period grating, making it difficult to achieve single-mode lasing

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