A. Müller, M. Maiwald and B. Sumpf

Published in:

J. Phys. Commun., vol. 6, no. 12, pp. 125007, doi:10.1088/2399-6528/acac6e (2022).

Abstract:

785 nm micro-integrated, dual-wavelength master oscillator power amplifiers with a footprint of 5 mm × 25 mm are presented. They are based on Y-branch distributed Bragg reflector ridge waveguide diode lasers and anti-reflection coated tapered amplifiers. In order to reduce the impact of potential optical feedback, devices with master oscillator front facet reflectivities of 5% and 30% as well as with an integrated miniaturized optical isolator have been realized. A comparison up to 1 W shows narrowband dual wavelength laser emission with a spectral distance of 0.6 nm (10 cm⁻¹) and individual spectral widths<20 pm. As expected, a higher front facet reflectivity leads to a significant reduction of feedback related mode hops. Longitudinal modes corresponding to the master oscillator resonator length remain within spectral windows <0.15 nm (3 cm⁻¹), suitable for applications such as Raman spectroscopy and especially shifted excitation Raman difference spectroscopy. Integrating a compact 30 dB optical isolator completely eliminates the observed optical feedback effects. Lateral beam propagation ratios of 1.2 (1/e²) enable easy beam shaping and fiber coupling. Outside of the experimental comparison, the developed MOPAs provide up to 2.7 W of optical output power available for applications.

Keywords:

master oscillator power amplifier, diode laser, distributed Bragg reflector, tapered amplifier, dual-wavelength, Raman spectroscopy

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