Abstract
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 H13CN at the C-band, analyzing the attainable signal-to-noise ratio for a range of averaging times.
Highlights
Since the beginning of the century, optical frequency comb (OFC) technology has revolutionized the field of optical metrology [1,2,3], finding applications in a plethora of fields, including molecular spectroscopy, telecommunications, astronomy and remote sensing, to cite just a few [4,5,6,7,8]
We have demonstrated a dual-comb system that combines pulsed GS and optical injection (OI) to perform spectroscopy measurements with a frequency spacing of 100 MHz
As is inherent in dual-comb spectroscopy (DCS), this optical bandwidth can be measured with a slow-speed digitizer, thanks to a very efficient frequency down-conversion into the RF domain
Summary
Since the beginning of the century, optical frequency comb (OFC) technology has revolutionized the field of optical metrology [1,2,3], finding applications in a plethora of fields, including molecular spectroscopy, telecommunications, astronomy and remote sensing, to cite just a few [4,5,6,7,8]. In parallel to the search for innovative applications, many efforts have been devoted to develop alternatives to mode-locked OFCs, with the aim of providing tunable, cost-efficient and field-deployable comb generators [9,10,11]. Among these comb platforms, OFCs generated from semiconductor lasers by gain-switching (GS) have attracted considerable attention in recent years [12,13,14,15,16,17,18,19,20,21,22,23,24,25,26]. When applied to DCS, gain-switched OFCs offer simple and tunable control of the difference between the line spacing of the combs, no need of nonlinear broadening to ensure comb overlap and a potential implementation from visible to mid-infrared [24]
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