Figure - PMC

Skip to main content

An official website of the United States government

Here's how you know

Here's how you know

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

View full-text article in PMC

. 2017 Dec 20;8:2216. doi: 10.1038/s41467-017-02392-5

Search in PMC
Search in PubMed
View in NLM Catalog
Add to search

© The Author(s) 2017

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

PMC Copyright notice

Fig. 4 — Applications of resonance modulation spectroscopy. a Gas sensing demonstration, where an HF absorption line at 1312.591 nm is measured in transmission using the resonance modulation scheme previously described. Voltage was translated into wavelength using a calibration curve obtained from independent PL cavity mode tuning data. A superluminescent diode (SLED) fiber-coupled to an HF gas cell (at p = 50 Torr), and filtered with a 12 nm wide 1310 nm band pass filter is used for excitation. A filter is needed to isolate a single absorption line, and a single cavity mode; inset: optical spectrum analyzer (OSA) spectrum of the SLED with the HF cell inserted, showing the same absorption line. b Wavemeter measurement of a FBG resonance in reflection performed using the resonance modulation scheme. A SLED is connected to the first input of a 2 × 2 fiber beam-splitter with the FBG on one of the outputs, and the second input (reflection) is coupled to the cavity through a NA = 0.45 objective (P _in ≈ 1.6 μW). The FBG peak (100 pm wide) is read by sweeping a cavity mode (δλ _c = 237 pm, δV _c = 270 mV), having a sensitivity (slope at zero crossing) of S _I = 3.53 nA V⁻¹. The noise measured at the zero crossing is δI _noise = 3.6 pA Hz^−1/2 that translates to a peak wavelength uncertainty of δλ _noise = (δI _noise/S _I) × (δλ _c /δV _c) = 0.9 pm Hz^−1/2. Inset left: the OSA spectrum of the FBG filter in reflection. Inset right: detuning of the FBG peak (left axis) and corresponding temperature shift (right axis) over a period of 120 s measured using the cavity sensor. The peak visible at t = 10 s is induced by convective heating from a heat-gun 50 cm away from the FBG. The current signal (lock-in output) is translated to displacement (∆λ) using the slope S _I. The FBG temperature sensitivity is taken to be δλ _B /δT = 8.5 pm K⁻¹ (specified by the manufacturer)