# Thermo-optical bistability in silicon micro-cantilevers

### Submission summary

 As Contributors: Ludovic Bellon Preprint link: scipost_202104_00023v1 Data repository: https://doi.org/10.5281/zenodo.4703792 Date accepted: 2021-05-17 Date submitted: 2021-04-20 15:03 Submitted by: Bellon, Ludovic Submitted to: SciPost Physics Academic field: Physics Specialties: Atomic, Molecular and Optical Physics - Experiment Condensed Matter Physics - Experiment Approach: Experimental

### Abstract

We report a thermo-optical bistability observed in silicon micro-cantilevers irradiated by a laser beam with mW powers: reflectivity, transmissivity, absorption, and temperature can change by a factor of two between two stable states for the same input power. The temperature dependency of the absorption at the origin of the bistability results from interferences between internal reflections in the cantilever thickness, acting as a lossy Fabry-Pérot cavity. A theoretical model describing the thermo-optical coupling is presented. The experimental results obtained for silicon cantilevers irradiated in vacuum at two different visible wavelengths are in quantitative agreement with the predictions of this model.

Published as SciPost Phys. 10, 120 (2021)

We thank the referees for their positive evaluations of our manuscript. We have provided a point by point answer to all the concerns they raised, and all are taken into account in the revised manuscript. For convenience, the uploaded preprint highlights the differences between the previous and current version of the manuscript (struck red : removed, blue : added), while arXiv:2101.12157v2 corresponds to the final manuscript.

### List of changes

1. First sentence of section 2 has been edited : **For visible light, silicon is neither transparent nor a good mirror** instead of *Silicon is a poor mirror for visible light*.
2. A paragraph has been added at the end of section 3.1 (end of page 4, top of page 5) to describe to finesse and quality factor of the optical cavity.
3. A paragraph has been added after eq. 6 (top of page 6) to describe the link between the optical cavity resonance and the optical-coupling feedback sign.
4. Figure 6 has been edited for enhanced readability
5. The evaluation of $H$ has been clarified in the first paragraph of section 5 (page 12) : the thickness it is now clearly identified has a fitting parameter of the model, and notations $H_{14}$ and $H_{28}$ are introduced for the 2 different samples.
6. Samples names are now **C14** and **C28** instead of *H14* and *H28*.
7. A footnote has been added in the last paragraph of section 5 (page 13) to comment on the dependency on temperature of the thermal conductivity reduction by confinement.
8. A paragraph has been added to the conclusion (page 14) to describe optimisation leads to trigger the bistability at lower input powers, and reduce the response time of the system.
9. The last sentences of the conclusion (page 15) have been edited to nuance the perspectives on heat flux sensing with "infinite" sensitivity.