Fringe locking type holographic interference photoetching system and fringe locking method

Abstract

The invention belongs to the technical field of information optics, and relates to a holographic interference photoetching system. In order to solve the problem that the interference fringe drift holographic grating contrast ratio decreases, a first high-speed photoelectric detector is utilized to acquire a moire fringe light intensity signal on the surface of a reference grating, and transmit thelight intensity signal to a single chip computer and a PID controller at the same time; a second high-speed photoelectric detector monitors a light intensity signal of a laser through a light beam sampling grating, the light intensity signal is transmitted to the single chip computer, and a signal output end of the PID controller transmits to a frequency modulation input end of a first ultrasonicgenerator; and when the PID controller judges that the light intensity signal detected in real time by the first high-speed photoelectric detector changes, the PID controller outputs a feedback signal to the first ultrasonic generator, the frequency of the first ultrasonic generator changes correspondingly, the phase of the -1 level diffraction light of a first acoustic optical modulator changes,accordingly the phase of the moire fringe is locked, and locking of the interference fringe phase is achieved.

Description

technical field [0001] The invention belongs to the technical field of information optics and relates to a holographic interference photolithography system. Background technique [0002] When shooting a large-scale holographic grating, a long exposure time is required due to the weak shooting light intensity. However, external vibration, air flow, temperature fluctuation and other factors will change the relative phase of the object light and reference light, and the interference fringes formed by them will drift randomly, thus reducing the contrast of the recording fringes. None of the current holographic lithography systems can solve the problem of interference fringe drift over a long period of time. Therefore, for long-term exposure, active vibration isolation methods are required to control the drift of interference fringes. The current existing fringe locking method: the invention patent with the patent number of 2006100399676 discloses the linear array CCD fitting fr...

AI Technical Summary

Problems solved by technology

[0003] In order to solve the technical problem of the random drift of the interference fringes during long-time moving exposure, which leads to the decrease of the contrast of the recording fringes, the present invention proposes a fringe-locked holographic interference lithography system, including a laser, a beam sampling grating, a half-wave plate, a beam splitting prism, the first A plane mirror, a second plane mirror, a third plane mirror, a first acousto-optic modulator, a first ultrasonic generator, a second acousto-optic modulator, a second ultrasonic generator, a first spatial filter, a second Two spatial filters, the first collimator lens, the second collimator lens, the grating substrate to be exposed, the reference grating, the first high-speed photodetector, the second high-speed photodetector, PID controller, single-chip microcomputer; the reference The grating is set on the grating substrate to be exposed, and the surface of the reference grating is in the same plane as the surface of the grating substrate to be exposed; the light emitted by the laser passes through the beam sampling grating, and its 0th-order transmitted and diffracted light enters the beam splitting prism to be divided into transmitted beam and reflected beam. The light beam, where the transmitted light beam passes through the half-wave plate, then passes through the first plane mirror and the second plane mirror, enters the first acousto-optic modulator, and the -1 order diffracted light of the first acousto-optic modulator enters the first spatial filter , then pass through the first collimator lens, expand the beam into parallel light, and finally project it onto the grating substrate to be exposed and the reference grating; the reflected beam passes through the third plane mirror, enters the second acousto-optic modulator, and the second acousto-optic modulator The -1st-order diffracted light of the filter enters the second spatial filter, then passes through the second collimator lens, expands the beam into parallel light, and finally projects on the grating substrate to be exposed and the reference grating; the transmitted beam and the reflected beam are on the exposed Interference on the surface of the grating substrate, and the interference light field of the transmitted beam and the reflected beam forms a virtual grating on the reference grating at the same time, and the direction of the virtual grating and the reference grating has a slight angle difference to form Moiré fringes; the said The single-chip microcomputer is provided with a first input terminal, a second input terminal, a reference input terminal, and an output terminal; the PID controller is provided with a correction signal input terminal, an input terminal, and a PID signal output terminal; the first ultrasonic generator is provided with There are frequency modulation input terminals and output terminals; the second ultrasonic generator is provided with an output terminal; both the first acousto-optic modulator and the second acousto-optic modulator are provided with input terminals; the above-mentioned Moiré fringes are projected onto the first high-speed On the photodetector, its light intensity signal is simultaneously transmitted to the first input terminal of the microcontroller and the sensor signal input terminal of the PID controller; the light emitted by the laser passes through the beam sampling grating, and its first-order reflected and diffracted light enters the second high-speed photodetector , the light intensity signal is transmitted to the second input terminal of the single-chip microcomputer, and the signal output terminal of the PID controller is transmitted to the frequency modulation input terminal of the first ultrasonic generator; the output terminal of the first ultrasonic generator is connected to the input terminal of the first acousto-optic modulator terminal connection, the output terminal of the second ultrasonic generator is connected with the input terminal of the second acousto-optic modulator, when the light intensity signal transmitted to the first high-speed photodetector detection in the PID controller changes, the PID controller outputs a feedback signal to The first ultrasonic generator, the frequency of the first ultrasonic generator changes accordingly, and the phase of the -1 order diffracted light of the first acousto-optic modulator changes, thereby locking the phase of the Moiré fringe

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