In this work we demonstrate the capability of two gain-switched optically injected semiconductor lasers to perform high-resolution dual-comb spectroscopy. The use of low duty cycle pulse trains to gain switch the lasers, combined with optical injection, allows us to obtain flat-topped optical frequency combs with 350 optical lines (within 10 dB) spaced by 100 MHz. These frequency combs significantly improve the spectral resolution reported so far on dual-comb spectroscopy with gain-switched laser diodes. We evaluate the performance of our system by measuring the transmission profile of an absorption line of H 13 CN at the C-band, analyzing the attainable signal-to-noise ratio for a range of averaging times.
Dual-comb spectroscopy has become a topic of growing interest in recent years due to the advantages it offers in terms of frequency resolution, accuracy, acquisition speed, and signal-to-noise ratio, with respect to other existing spectroscopic techniques. In addition, its characteristic of mapping the optical frequencies into radio-frequency ranges opens up the possibility of using non-demanding digitizers. In this paper, we show that a low-cost software defined radio platform can be used as a receiver to obtain such signals accurately using a dual-comb spectrometer based on gain-switched semiconductor lasers. We compare its performance with that of a real-time digital oscilloscope, finding similar results for both digitizers. We measure an absorption line of a H 13 C 14 N cell and obtain that for an integration time of 1 s, the deviation obtained between the experimental data and the Voigt profile fitted to these data is around 0.97% using the low-cost digitizer while it is around 0.84% when using the high-end digitizer. The use of both technologies, semiconductor lasers and low-cost software defined radio platforms, can pave the way towards the development of cost-efficient dual-comb spectrometers.
We demonstrate a distance measurement system based on two gain-switched optical frequency combs which improves the ambiguity distance of these systems by using low repetition rates (100 MHz to 5 MHz).
We have designed, fabricated and characterized an indium phosphide photonic integrated circuit to be utilized as the transmitter of a differential absorption lidar for carbon dioxide sensing. We demonstrate its suitability for the application.
We combine optical injection and pulsed electrical excitation to generate flat-topped 100-MHz optical frequency combs from gain-switched semiconductor lasers. A highly coherent dual-comb system is tested by conducting high-resolution spectroscopy.
We demonstrate a dual-comb interferometer based on two externally densified gain-switching optical frequency combs and show its potential for ultra-high-resolution spectroscopy.
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