Slotted Y-branch laser for cw-THz thickness measurements at 1 THz

Nils Surkamp; Alexandra Gerling; James O'Gorman; Martin Honsberg; Sebastian Schmidtmann; Uttam Nandi; Sascha Preu; Joachim Sacher; Carsten Brenner; Martin R. Hofmann

doi:10.1117/12.2609787

3 March 2022 Slotted Y-branch laser for cw-THz thickness measurements at 1 THz

Nils Surkamp, Alexandra Gerling, James O'Gorman, Martin Honsberg, Sebastian Schmidtmann, Uttam Nandi, Sascha Preu, Joachim Sacher, Carsten Brenner, Martin R. Hofmann

Author Affiliations +

Proceedings Volume 12021, Novel In-Plane Semiconductor Lasers XXI; 1202104 (2022) https://doi.org/10.1117/12.2609787
Event: SPIE OPTO, 2022, San Francisco, California, United States

Abstract

This work investigates a monolithic slotted Y-branch diode laser as a beating source to drive a continuous wave Terahertz spectrometer. Both arms of the Y-branch laser exhibit spectral selective feedback, which causes simultaneous emission at two frequencies. At first, a thorough optical characterisation with 5400 individual setpoints is performed to find the best point of operation. Two operational regimes with difference frequencies of 1 THz ± 10.5 GHz and 0.85 THz ± 6.5 GHz were identified. While validating the laser as a beating source to drive a cw-THz spectrometer, it was demonstrated that the device supports current-induced tuning of the emitted difference frequency. This technique allows frequency sweeps in the terahertz regime that can be used to measure the transmitted field without a mechanical delay stage. Finally, this technique is demonstrated to independently determine the thickness and refractive index of high resistive float zone silicon wafers of 2, 3.5, 4 and 8 mm thickness without a priori knowledge.

Conference Presentation

Citation Download Citation

Nils Surkamp, Alexandra Gerling, James O'Gorman, Martin Honsberg, Sebastian Schmidtmann, Uttam Nandi, Sascha Preu, Joachim Sacher, Carsten Brenner, and Martin R. Hofmann "Slotted Y-branch laser for cw-THz thickness measurements at 1 THz", Proc. SPIE 12021, Novel In-Plane Semiconductor Lasers XXI, 1202104 (3 March 2022); https://doi.org/10.1117/12.2609787

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