Whispering gallery mode sensing with a dual frequency comb probe

Abstract

Silica microspheres are probed with a dual comb interferometry setup. The impulse responses of these microresonators are measured with a temporal resolution smaller than 400 fs over more than 200 ps. The amplitudes and phases of the impulse responses are interpreted as providing sensing information. The more familiar transmission spectra corresponding to the measured impulse responses are also calculated and shown. Sensing is demonstrated by varying the concentration of isopropanol in de-ionized water surrounding the microsphere and by binding bovine serum albumin on the silanized microsphere surface.

Dual-comb spectroscopy

“…Although we focus here on DCS applied to linear spectroscopy as a broadband coherent system, the same basic technique has been applied to closely related applications. The ability to simultaneously record loss and dispersion has made dual-comb approaches attractive for characterizing telecom components, fiber gratings, and microresonators [78][79][80]. A modified dual-comb system can monitor active sources such as static and fast-swept cw waveforms [81][82][83][84], arbitrary optical waveforms [57,85,86], and even pulsed or incoherent sources [87,88].…”

Controling the coupling properties of active ultrahigh-Q WGM microcavities from undercoupling to selective amplification

“…In a similar manner, the ringing signal from the cavity, is used to infer the coupling regime for a passive resonator30. Note that in the stationary regime this can be done unambiguously solely by interferometric444546 or polarimetric474849 techniques. For a perfectly transparent cavity (lossless cavity τ 0 → +∞), the power transmission is T ( ω ) = 1 as can be seen in Fig.…”

Continuous real-time correction and averaging for frequency comb interferometry

“…Coherent averaging with the combs allows a great sensitivity over a large spectral range, thus addressing several resonator modes in a short time. Figure 6 shows a 10 second measurement of a 200 µm silica microsphere in the same configuration as described in Michaud-Belleau's [18] paper. The impulse response in Fig.…”

“…The IGMs sampled by the ADC were chirped to lower the dynamic range needed. This chirp can be numerically removed by post-processing to recover the impulse response of the sample [18]. Once the chirp is removed, the IGM (see Fig.…”

“…The second measurement to demonstrate the potential of this technique is of a silica micro-resonator cavity. Cavity ring down in high Q-factor micro cavities is of interest for biodetection [18]. Coherent averaging with the combs allows a great sensitivity over a large spectral range, thus addressing several resonator modes in a short time.…”