Silicon-chip-based mid-infrared dual-comb spectroscopy

Publication Type:

Journal Article

Source:

arXiv:1610.01121 (2016)

URL:

https://arxiv.org/abs/1610.01121

Abstract:

<p>On-chip spectroscopy that could realize real-time fingerprinting with label-free and high-throughput detection of trace molecules is one of the 'holy grails" of sensing. Such miniaturized spectrometers would greatly enable applications in chemistry, bio-medicine, material science or space instrumentation, such as hyperspectral microscopy of live cells or pharmaceutical quality control. Dual-comb spectroscopy (DCS), a recent technique of Fourier transform spectroscopy without moving parts, is particularly promising since it measures high-precision spectra in the gas phase using only a single detector. Here, we present a microresonator-based platform designed for mid-infrared (mid-IR) DCS. A single continuous-wave (CW) low-power pump source generates two mutually coherent mode-locked frequency combs spanning from 2.6 <span class="MathJax_Preview"></span><span id="MathJax-Element-1-Frame" class="MathJax"><span id="MathJax-Span-1" style="width: 0.712em; display: inline-block;" class="math"><span style="display: inline-block; position: relative; width: 0.538em; height: 0px; font-size: 129%;"><span style="position: absolute; clip: rect(1.994em, 1000.49em, 2.95em, -1000em); top: -2.584em; left: 0em;"><span id="MathJax-Span-2" class="mrow"><span id="MathJax-Span-3" style="font-family: STIXGeneral; font-style: italic;" class="mi">μ</span></span><span style="display: inline-block; width: 0px; height: 2.584em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.334em; border-left: 0px solid; width: 0px; height: 0.955em;"></span></span></span>m to 4.1 <span class="MathJax_Preview"></span><span id="MathJax-Element-2-Frame" class="MathJax"><span id="MathJax-Span-4" style="width: 0.712em; display: inline-block;" class="math"><span style="display: inline-block; position: relative; width: 0.538em; height: 0px; font-size: 129%;"><span style="position: absolute; clip: rect(1.994em, 1000.49em, 2.95em, -1000em); top: -2.584em; left: 0em;"><span id="MathJax-Span-5" class="mrow"><span id="MathJax-Span-6" style="font-family: STIXGeneral; font-style: italic;" class="mi">μ</span></span><span style="display: inline-block; width: 0px; height: 2.584em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.334em; border-left: 0px solid; width: 0px; height: 0.955em;"></span></span></span>m in two silicon micro-resonators. Thermal control and free-carrier injection control modelocking of each comb and tune the dual-comb parameters. The large line spacing of the combs (127 GHz) and its precise tuning over tens of MHz, unique features of chip-scale comb generators, are exploited for a proof-of-principle experiment of vibrational absorption DCS in the liquid phase, with spectra of acetone spanning from 2870 nm to 3170 nm at 127-GHz (4.2-cm<span class="MathJax_Preview"></span><span id="MathJax-Element-3-Frame" class="MathJax"><span id="MathJax-Span-7" style="width: 1.198em; display: inline-block;" class="math"><span style="display: inline-block; position: relative; width: 0.915em; height: 0px; font-size: 129%;"><span style="position: absolute; clip: rect(0.02em, 1000.91em, 1.184em, -1000em); top: -1.023em; left: 0em;"><span id="MathJax-Span-8" class="mrow"><span id="MathJax-Span-9" class="msubsup"><span style="display: inline-block; position: relative; width: 0.913em; height: 0px;"><span style="position: absolute; clip: rect(3.822em, 1000em, 4.145em, -1000em); top: -3.984em; left: 0em;"><span id="MathJax-Span-10" class="mi"></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span><span style="position: absolute; top: -4.347em; left: 0em;"><span id="MathJax-Span-11" class="texatom"><span id="MathJax-Span-12" class="mrow"><span id="MathJax-Span-13" style="font-size: 70.7%; font-family: STIXGeneral;" class="mo">−</span><span id="MathJax-Span-14" style="font-size: 70.7%; font-family: STIXGeneral;" class="mn">1</span></span></span><span style="display: inline-block; width: 0px; height: 3.984em;"></span></span></span></span></span><span style="display: inline-block; width: 0px; height: 1.023em;"></span></span></span><span style="display: inline-block; overflow: hidden; vertical-align: -0.069em; border-left: 0px solid; width: 0px; height: 1.224em;"></span></span></span>) resolution. We take a significant step towards a broadband, mid-IR spectroscopy instrument on a chip. With further system development, our concept holds promise for real-time and time-resolved spectral acquisition on the nanosecond time scale.</p>

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