Modulated DFB ridge laser diodes at 894 nm for compact Cesium CPT atomic clocks

M. Krakowski; M. Meghnagi; P. Afuso-Roxo; B. Vinter; F. Duport; F. Van Dijk; A. Larrue; C. Theveneau; E. Vinet; Y. Robert; J.P. Legoec; M. Garcia; O. Parillaud; B. Gerard

doi:10.1117/12.2650266

15 March 2023 Modulated DFB ridge laser diodes at 894 nm for compact Cesium CPT atomic clocks

M. Krakowski, M. Meghnagi, P. Afuso-Roxo, B. Vinter, F. Duport, F. Van Dijk, A. Larrue, C. Theveneau, E. Vinet, Y. Robert, J.P. Legoec, M. Garcia, O. Parillaud, B. Gerard

Author Affiliations +

Proceedings Volume 12440, Novel In-Plane Semiconductor Lasers XXII; 1244004 (2023) https://doi.org/10.1117/12.2650266
Event: SPIE OPTO, 2023, San Francisco, California, United States

Abstract

Time and Frequency applications, such as time synchronization of complex networks, are in need of high accuracy and stability clocks. Optically pumped Cesium tube atomic clocks satisfy these demands. However, Size, Weight and Power (SWaP) are very important parameters considering easier implementation of atomic clocks in systems. The innovative principal of Coherent Population Trapping (CPT) clocks can meet these challenges. They require a 894nm (Cs D1 line) DFB laser modulated at half the clock frequency (4.6GHz). The modulation generates the side bands separated by 9.2GHz. The laser should also keep a linewidth below 1MHz. We grow the layers of our laser structure two steps Metal Organic Vapor Phase Epitaxy, with an Aluminum free active region. It includes a single GaInAsP compressively strained Quantum Well (QW) and a GaInP waveguide, on GaAs substrates. The use of Al free materials allows for the realization of a buried Bragg grating which induces a very stable single frequency operation as a function of current and temperature. We have investigated our actual 2mm long laser in light current characteristics, optical spectra, linewidth and direct modulation, showing high stability at different temperatures. The Cs D1 line is achieved near room temperature with a very high SMSR (50dB) and a low linewidth (<1MHz). The actual -3dB bandwidth is 2.3GHz at 80mA (48mW) at 25°C. We have designed a new laser structure allowing 10 GHz bandwidth, without reducing the cavity length.

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M. Krakowski, M. Meghnagi, P. Afuso-Roxo, B. Vinter, F. Duport, F. Van Dijk, A. Larrue, C. Theveneau, E. Vinet, Y. Robert, J.P. Legoec, M. Garcia, O. Parillaud, and B. Gerard "Modulated DFB ridge laser diodes at 894 nm for compact Cesium CPT atomic clocks", Proc. SPIE 12440, Novel In-Plane Semiconductor Lasers XXII, 1244004 (15 March 2023); https://doi.org/10.1117/12.2650266

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