M. Chi^a, A. Müller^b, A.K. Hansen^a, O.B. Jensen^a, P.M. Petersen^a, B. Sumpf^b

Published in:

Opt. Commun., vol. 514, pp. 128120 (2022).

Abstract:

Solar radiation is a challenge for laser-based daylight imaging since it decreases the signal-to-noise ratio (SNR) of the imaging. Here we demonstrate a micro-integrated external-cavity tapered diode laser system for daylight imaging. It emits light at a wavelength of 762 nm, chosen because of its overlap with an oxygen absorption band in the solar radiation spectrum. The integrated laser system consists of a tapered diode amplifier as gain medium and an external volume Bragg grating for spectrum stabilization and narrowing, thus a narrow bandpass optical filter can be used to improve the SNR further. The laser system can be operated in both continuous wave (CW) mode and pulsed mode by modulating the injected current to the amplifier. In CW mode operation, 1.3 W of output power is obtained with an emission spectral linewidth of 4 pm, and a beam propagation factor in the slow axis, M², of 1.7 (4σ). In pulsed mode operation with a trigger signal of a 50 µs pulse width and a 10 kHz repetition rate, 2.0 W of peak output power is achieved with an emission spectral bandwidth of 0.2 nm, and an M² in the slow axis of 1.9 (4σ). The modulation depth is almost 100%.

Keywords:

Tapered diode laser, Micro-integrated, External-cavity, 762 nm, Daylight imaging

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