N/A

The purpose of the GNS system is to measure the mechanical loss of SiN and SiON films in our laboratory. These films will ultimately be used as mirror coatings in the large Michelson interferometer of the gravitational wave observatory LIGO Voyager. Since the operating temperature is 123K, we need to understand the performance of the films in low-temperature environments to meet the requirements.
The study is divided into three main parts. The first part introduces the establishment of the GNS system. Including the measurement principles, vibration methods, and the resonant modes simulated by COMSOL. The experiment uses a commonly seen Michelson interferometer, which is slightly 0000modified for measurement purposes. The second part utilizes the GNS system to measure the resonance frequency of silicon wafers and the ringdown results at each frequency. We can deduce the Young's modulus of the sample from the measured single resonance frequency. By inputting this value into COMSOL, we can obtain more accurate simulation results. The third part tests the cooling rate of the GNS system in the low-temperature setup we established. We connect the GNS to the cryogenic chamber through a sidepod to test the cooling rate and final temperature of the wafer. By improving the thermal conductivity of the system with heat links, we aim to achieve a temperature of 123K.

[1] A. Einstein, “Die grundlage der allgemeinen relativitatstheorie”, Annalen der Physik 49, 769 (1916)
[2] B. P. Abbott et al., Observation of Gravitational Waves from a Binary Black Hole Merger, PRL, 116, 061102 (2016)
[3] LIGO Scientific Collaboration Group. Instrument science white paper. LIGO- T1100309-v5: 7, Oct. 2011.
[4] H. B. Callen, T. A. Weltont. Irreversibility and generalized noise. Phys. Rev., Jul. 83,34-40 (1951)
[5] R. F. Greene, H. B. Callen. On the formalism of thermodynamic fluctuation theory. Phys. Rev., 83 : 1231-1235 (1951)
[6] H. B. Callen, R. F. Greene, On a theorem of irreversible thermodynamics., Phys. Rev. 86,702-710 (1952)
[7] A. Einstein, “On the movement of small particles suspended in a stationary liquid demanded by the molecular-kinetic theory of heat”, Annalen der Physik 17, 549. (1900)
[8] Y. Levin, “Internal thermal noise in the LIGO test masses: A direct approach”. Phys. Rev. D 57, 659 (1998).
[9] H. W. Pan, Study of silicon nitride and silica films fabricated by a plasma enhanced chemical vapor deposition method for low thermal noise mirror coating of laser interferometer gravitational wave detectors. PhD Thesis, National Tsing Hua University (2018).
[10] Nicholas A. Didio, Cryogenic Mechanical Loss Studies of Large-Area Substrate-Transferred GaAs/AlGaAs Crystalline Coatings. LIGO-P2300050-v8
[11] Nicholas A. Didio, AlGaAs coating studies for present and future gravitational wave detectors. LIGO-P2300084-v1
[12] https://reurl.cc/GA2exy
[13] N. C. Kang, Photothermal common-path interferometry system setup and study of the optical absorption of the silicon nitride films deposited by PECVD method
[14] Z. Y. Wang, Developing a Gentle Nodal Suspension system for measuring mechanical loss. (2024)
[15] C. Y. Lin, Measurements of mechanical loss in SiN deposited on a cantilever using the low-pressure chemical vapor deposition (LPCVD) method and developing a Gentle Nodal Suspension (GNS) for measuring mechanical loss. (2023)
[16] 李正中,”薄膜光學與鍍膜技術”,第七版,藝軒圖書出版社(2012)..
[17] 麥克遜干涉 (nthu.edu.tw) http://www.phys.nthu.edu.tw/~gplab/file/Michelson%20interference/Michelson%20interference.pdf
[18] Stephen E, Bialkowski and Agnes Chartier. Diffraction effects in single-and two-
laser photothermal lens spectroscopy. Appl. Opt. Vol. 36, No. 27, 6711-6721 (1997).
[19] Bahaa E. A. Saleh, Malvin Carl Teich,‘‘Fundamentals of photonic,’’John
Wiley&Sons, 1991
[20] Cristine A. Carter and Joel M. Harris. Comparison of models describing the
thermal lens effect. Appl. Opt. Vol. 23, No. 3, 476-481 (1983)
[21] A. L. Alexandrovski, Martin Fejer, Roger Route, Optical absorption measurement
in sapphire, LIGO document:G000242-00-D
[22] A. L. Alexandrovski, M. M. Fejer, A. Markosyan, Photothermal common-path
interferometry(PCI): New developments, Proc. SPIE 7193 (2009)
[23] Gupta, Shefali, et al. "Optimizing the performance of MEMS electrostatic comb drive actuator with different flexure springs." Proceedings of the 2012 COMSOL conference. Bangalore. 2012.