The Australian National University

Malcolm Bruce Gray

Jong Hann Chow

David Ernest McClelland

Daniel Anthony Shaddock

Ian C M Littler

Ian Charles Murray Littler

A system and method for stabilizing a plurality of output frequencies (wavelengths) of a plurality of lasers (). The laser beams are combined using optical multiplexer () and coupled into length-imbalanced (armlength-mismatched) Mach-Zehnder interferometer (MZI) () having an optical modulator (e.g. AOM) () in one of its arms. The output of the MZI is divided into corresponding beams via optical demultiplexer () and each beam is detected by a respective photo-diode (PD) (). The individual electric signals, so generated, are demodulated using a corresponding plurality of phase-responsive devices () and the resulting phase-signals are directed to a plurality of servo-controllers () to control the central frequency of the respective lasers () via a corresponding plurality of feedback loop circuits (). The lasers () can have different central frequencies which can also be individually tunned using offset modules () in the phase-responsive devices ().

Methods and systems for frequency stabilisation of multiple lasers

A system and method for spectroscopic detection of loss in a resonator cavity is disclosed. The system can include a number of components. A tunable laser source can generate a laser beam. A frequency locking system can lock the frequency of the laser beam to a resonance of the resonator cavity or lock the length of the cavity to the frequency of the laser beam. The first modulation element can modulate the laser beam at a first modulation frequency to generate a modulated laser beam. The input coupler can direct the modulated laser beam into the resonator cavity. The first directing element can direct a first portion of light reflected from the input coupler to a first photodetector. The first demodulator can demodulate the first modulation signal to generate a first error signal which is a function of the loss in the resonator cavity.

Spectroscopic detection system and method

An apparatus for interferometric sensing, comprising a plurality of single-longitudinal mode laser sources to each provide radiation at a corresponding plurality of selected wavelengths, and at least one modulator to frequency or phase modulate the radiation from each laser; a plurality of Fabry-Perot interferometers formed by Bragg Gratings written into optical fibre, each interferometer being responsive to one of the said plurality of wavelengths to each produce a reflected or transmitted optical output signal dependent on the corresponding interferometer path length; and one or more demodulators to demodulate the optical output signals and produce a corresponding plurality of measurement signals indicative of optical path lengths of the respective interferometers.

Apparatus for interferometric sensing

This invention provides a method and an optical system for sensing and controlling the frequency for a laser with respect to an optical cavity and for sensing and controlling the length difference of interferometer paths in a two beam interferometer. A misalignment is introduced in the incident laser radiation to produce a fundamental mode (TEM ) in the cavity or interferometer and the reflection of a least one higher order mode (TEM ). A split photodetector ( ) allows the interference between these two modes to be measured separately by detecting two spatially distinct portions of the single reflected beam. An error signal indicative of the difference between the fundamental mode frequency and the cavity resonant frequency is obtained by substracting the outputs from the two parts of the photodetector.

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Pennant Hills, Australia

Malcolm Bruce Gray