Abstract
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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sup> C <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sup> 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.
Highlights
O PTICAL Frequency Combs (OFCs) have attracted a lot of attention during the last decades due to their vast number of applications in many different fields [1]
In the field of molecular spectroscopy, dual-comb spectroscopy (DCS) has become one of the most appealing techniques since it offers advantages over conventional spectrometers such as the absence of moving parts, the improvement of frequency resolution, accuracy, acquisition speed, and signal-to-noise ratio (SNR), as well as a great potential to be implemented in compact systems [8]
Each slave laser is driven with the superposition of a DC bias current IDC and an AC pulse train generated by a pulse pattern generator (PPG) (Anritsu MU181020A) with peak-to-peak voltage amplitude V AC, repetition rate fR, repetition rate difference ∆fR and pulse width tpulse
Summary
O PTICAL Frequency Combs (OFCs) have attracted a lot of attention during the last decades due to their vast number of applications in many different fields [1]. OFCs have been found especially suitable for applications such as molecular spectroscopy [2], telecommunications [3], radio-frequency (RF) generation [4] and distance measurement [5]–[7] among others. The basic concept of DCS, which is depicted, consists in using two OFCs with slightly different repetition frequencies (fR and fR + ∆fR) that interact with an absorbent medium before interfering in a photodiode, where they generate an electrical RF comb [9]. The result is a RF comb that maps the absorption that takes place in the optical frequency range into a down-converted electrical frequency range, making the measurements simpler
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