= Optical spring =

==  Members ==

 * Kentaro Komori
 * Yuta Michimura
 * Nobuyuki Matsumoto
 * Yoichi Aso
 * Masaki Ando

==  Overview ==

Radiation pressure of laser light in an optical cavity acts on the mirror's mechanical motion as restoring force when the cavity is detuning. This effect is called optical spring. It's useful for improving sensitivity of gravitational detectors and for research of opto-mechanics. The optical spring has potential to beat SQL in the detector sensitivity and to give light on macroscopic quantum mechanics.

==  Current status ==

In Ando group the optical spring effect is developed with a 5 mg mirror consisting of a triangle cavity. We have succeeded in increasing the resonant frequency of the pendulum mode from 2 Hz up to 1 kHz and cooling the mode to 15 mK.

[[attachment:5mgpendulumzoom.png|{{attachment:5mgpendulumzoom.png|5mgpendulumzoom|width="500"}}]]
[[attachment:remotecoolingresult.png|{{attachment:remotecoolingresult.png|remotecoolingresult|width="300"}}]]
[[attachment:cooling1kHz.png|{{attachment:cooling1kHz.png|cooling1kHz|width="300"}}]]

==  Related papers ==
 * [[https://www.osapublishing.org/oe/abstract.cfm?uri=oe-22-11-12915|Nobuyuki Matsumoto, Yuta Michimura, Yoichi Aso, Kimio Tsubono, Optically trapped mirror for reaching the standard quantum limit, Optics Express 22, 12915 (2014)]]
 * [[http://journals.aps.org/pra/abstract/10.1103/PhysRevA.92.033825|Nobuyuki Matsumoto, Kentaro Komori, Yuta Michimura, Gen Hayase, Yoichi Aso, Kimio Tsubono, 5-mg suspended mirror driven by measurement-induced backaction, Phys. Rev. A 92, 033825 (2015)]]
 * [[http://journals.aps.org/pra/abstract/10.1103/PhysRevA.94.033822|Nobuyuki Matsumoto, Kentaro Komori, Sosuke Ito, Yuta Michimura, Yoichi Aso, Direct measurement of optical-trap-induced decoherence, Phys. Rev. A 94, 033822 (2016)]]
 * [[http://www.springer.com/jp/book/9784431558804|Nobuyuki Matsumoto, Direct Measurement of Quantum Back-Action in a Macroscopic System, PhD thesis, The University of Tokyo (2013)]]
 * [[http://t-munu.phys.s.u-tokyo.ac.jp/theses/komori_m.pdf|Kentaro Komori, Remote Optical Cooling of a Massive Oscillator, Master thesis, The University of Tokyo (2015)]]