Laser Sources & Development

[IMAGE: Optical table with a multi-stage laser amplifier chain, mirrors, Faraday isolators, and diagnostic beam splitters, all mounted in black anodised optomechanics]

Figure 1: The single-frequency Nd:YAG MOPA system on an actively-isolated optical table in Building 1. The master oscillator (front left) is a non-planar ring oscillator (NPRO) injection-seeded for single-longitudinal-mode operation. Two amplifier stages are visible on the right side of the table.

Overview

The Laser Sources programme designs, builds, and characterises custom laser systems for Institute projects and for collaborative programmes with external partners. Emphasis is on single-frequency operation, wavelength agility, and long-term stability for deployment in demanding measurement environments.

Active Projects

Single-Frequency Nd:YAG MOPA

A master-oscillator power-amplifier system delivering 25 W CW at 1064 nm with a measured linewidth below 5 kHz over 10 ms integration. The oscillator stage uses a monolithic non-planar ring oscillator (NPRO) for intrinsic single-frequency stability. Two diode-pumped amplifier stages provide gain while preserving the seed linewidth through careful attention to ASE suppression and thermal lensing management. Frequency-doubling in periodically-poled KTP yields 10 W at 532 nm.

The system serves as the transmitter source for the free-space optical communications programme and has been operated continuously for periods exceeding 500 hours without mode-hop or lock-loss events.

[IMAGE: False-colour beam profile image showing a symmetric Gaussian intensity distribution]

Figure 2: Output beam profile of the Nd:YAG MOPA captured on a CCD beam profiler, showing near-perfect TEM\u2080\u2080 mode quality. M\u00b2 measured at <1.05 in both axes.

CW Optical Parametric Oscillator

A singly-resonant continuous-wave OPO using a 40 mm periodically-poled lithium niobate (PPLN) crystal, pumped by the 532 nm output of the Nd:YAG MOPA. The idler wavelength is tunable from 2.5 to 4.5 μm by crystal temperature tuning (50–200°C) and grating-period selection. Idler output exceeds 1.5 W at the centre of the tuning range, with a linewidth below 100 kHz (free-running).

This source supports the mid-IR spectroscopic systems programme and has been used for trace-gas detection of CH₄, N₂O, and CO at ppb-level concentrations using cavity ring-down spectroscopy.

Ti:Sapphire Femtosecond System

A Kerr-lens mode-locked Ti:Sapphire oscillator producing pulses shorter than 50 fs at a repetition rate of 80 MHz, with a regenerative amplifier boosting pulse energy to 2 mJ at 1 kHz. The system is used for ultrafast pump-probe spectroscopy of semiconductor heterostructures and for THz generation via optical rectification in ZnTe, supporting the THz spectroscopy programme in the Electromagnetic Systems Division.

Related Publications

Tanaka A., Voss H. — "Development of a high-power single-frequency Nd:YAG laser for intersatellite communications." Proc. SPIE 4630, 112–120 (2002). [abstract]
Tanaka A. et al. — "Phase-locked diode laser array for coherent beam combining." Appl. Opt. 42, 5637–5643 (2003). [abstract]
Tanaka A., Voss H. — "Broadly tunable CW OPO for high-resolution mid-IR spectroscopy." Opt. Lett. (submitted, 2004). [abstract]

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