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Thermal tuning of a fiber-integrated Fabry-Pérot cavity

Clemens Singer, Alexander Goetz, Adarsh S. Prasad, Martin Becker, Manfred Rothhardt, Sarah M. Skoff

TL;DR

This work demonstrates thermal control of a fiber-integrated, alignment-free Fabry-Pérot cavity formed by two independently tunable fiber Bragg gratings. By stabilizing each grating's temperature, the authors achieve precise tuning of the cavity resonance and the individual stop bands, enabling post-fabrication finesse optimization and operation as a tunable, narrowband filter with a spectral width of $0.07 \pm 0.02$ pm and suppression above $-15$ dB. The study also quantifies the center-frequency shift via the Bragg wavelength's temperature dependence, showing linear shifts of several pm per kelvin for each grating and a total tunable range of roughly $160$ pm while maintaining high finesse ($F \sim 129 \pm 11$). This tunability supports reversible on/off cavity operation, facilitating reference measurements for solid-state quantum emitters and enabling versatile, alignment-free applications in quantum optics and photonics. The results highlight the practical potential of thermally-tunable, in-fiber cavities for coupling to solid-state emitters and for high-precision filtering in integrated photonics.

Abstract

Here, we present the thermal tuning capability of an alignment-free fiber-integrated Fabry-Pérot cavity.The two mirrors are made of fiber Bragg gratings that can be individually temperature stabilized and tuned. We show the temperature tuning of the resonance wavelength of the cavity without any degradation of the finesse and the tuning of the individual stop bands of the fiber Bragg gratings. This not only permits for the cavity's finesse to be optimized post-fabrication but also makes this cavity applicable as a narrowband filter with a FWHM spectral width of 0.07 (0.02) pm and a suppression of more than -15 dB that can be wavelength tuned. Further, in the field of quantum optics, where strong light-matter interactions are desirable, quantum emitters can be coupled to such a cavity and the cavity effect can be reversibly omitted and re-established. This is particularly useful when working with solid-state quantum emitters where such a reference measurement is often not possible once an emitter has been permanently deposited inside a cavity.

Thermal tuning of a fiber-integrated Fabry-Pérot cavity

TL;DR

This work demonstrates thermal control of a fiber-integrated, alignment-free Fabry-Pérot cavity formed by two independently tunable fiber Bragg gratings. By stabilizing each grating's temperature, the authors achieve precise tuning of the cavity resonance and the individual stop bands, enabling post-fabrication finesse optimization and operation as a tunable, narrowband filter with a spectral width of pm and suppression above dB. The study also quantifies the center-frequency shift via the Bragg wavelength's temperature dependence, showing linear shifts of several pm per kelvin for each grating and a total tunable range of roughly pm while maintaining high finesse (). This tunability supports reversible on/off cavity operation, facilitating reference measurements for solid-state quantum emitters and enabling versatile, alignment-free applications in quantum optics and photonics. The results highlight the practical potential of thermally-tunable, in-fiber cavities for coupling to solid-state emitters and for high-precision filtering in integrated photonics.

Abstract

Here, we present the thermal tuning capability of an alignment-free fiber-integrated Fabry-Pérot cavity.The two mirrors are made of fiber Bragg gratings that can be individually temperature stabilized and tuned. We show the temperature tuning of the resonance wavelength of the cavity without any degradation of the finesse and the tuning of the individual stop bands of the fiber Bragg gratings. This not only permits for the cavity's finesse to be optimized post-fabrication but also makes this cavity applicable as a narrowband filter with a FWHM spectral width of 0.07 (0.02) pm and a suppression of more than -15 dB that can be wavelength tuned. Further, in the field of quantum optics, where strong light-matter interactions are desirable, quantum emitters can be coupled to such a cavity and the cavity effect can be reversibly omitted and re-established. This is particularly useful when working with solid-state quantum emitters where such a reference measurement is often not possible once an emitter has been permanently deposited inside a cavity.

Paper Structure

This paper contains 8 sections, 2 equations, 5 figures.

Table of Contents

  1. Abstract
  2. Introduction
  3. Experimental Setup
  4. Results
  5. Individually tuning the stop bands of the two fiber Bragg gratings
  6. Tuning the center frequency of the cavity
  7. Conclusion
  8. Funding Information

Figures (5)

  • Figure 1: Fiber mount with (1) the thermistor in the hole of the top plate, (2) the Peltier element on the bottom and (3) the fiber itself.
  • Figure 2: Maximum finesse values (a) in transmission when grating one is heated from 10 to 60°C. With grating two, constantly held at 22°C.
  • Figure 3: Transmission spectra with grating two at 60°C (a) showing two separate stop bands, with grating one and two at room temperature (b) showing the finesse that is obtained without any temperature tuning and grating one at 37°C (c) showing best overlap. d) zoomed in region of transmission peaks at best overlap with an inset that shows the transmission plotted with a db scale to show functionality as a narrowband filter
  • Figure 4: Wavelength shift when (a) grating one and (b) grating two is heated. Fitted function in red.
  • Figure 5: Maximum finesse values as the center frequency of the cavity is temperature-tuned. The datapoints are the mean value of three measurements and the errorbars are the corresponding standard deviation