Korean Journal of Optics and Photonics (한국광학회지)

Optical Society of Korea (한국광학회)
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Linewidth Reduction of a Yellow Laser by a Super-cavity and the Measurement of the Cavity Finesse

초공진기를 이용한 노란색 레이저의 선폭 축소 및 초공진기의 예리도 측정

  • Lee, Won-Kyu (Center for Emerging Measurement Standards, Korea Research Institute of Standards and Science) ;
  • Park, Chang-Yong (Center for Emerging Measurement Standards, Korea Research Institute of Standards and Science) ;
  • Park, Sang-Eon (Center for Length and Time, Korea Research Institute of Standards and Science) ;
  • Ryu, Han-Young (Center for Length and Time, Korea Research Institute of Standards and Science) ;
  • Yu, Dai-Hyuk (Center for Emerging Measurement Standards, Korea Research Institute of Standards and Science) ;
  • Mun, Jong-Chul (Center for Emerging Measurement Standards, Korea Research Institute of Standards and Science) ;
  • Suh, Ho-Suhng (Center for Length and Time, Korea Research Institute of Standards and Science)
  • 이원규 (한국표준과학연구원 차세대표준연구단) ;
  • 박창용 (한국표준과학연구원 차세대표준연구단) ;
  • 박상언 (한국표준과학연구원 길이시간센터) ;
  • 유한영 (한국표준과학연구원 길이시간센터) ;
  • 유대혁 (한국표준과학연구원 차세대표준연구단) ;
  • 문종철 (한국표준과학연구원 차세대표준연구단) ;
  • 서호성 (한국표준과학연구원 길이시간센터)
  • Received : 2010.04.29
  • Accepted : 2010.05.26
  • Published : 2010.06.25
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Abstract

Sum frequency generation was utilized to obtain a yellow laser with the wavelength of 578.4 nm for a probe laser of an Yb lattice clock. The output of an Nd:YAG laser with wavelength of 1319 nm and that of an Yb-fiber laser with wavelength of 1030 nm were passed through a waveguided periodically-poled lithium niobate (WG-PPLN) for sum frequency generation. It is required that the probe laser has a linewidth of the order of 1 Hz to fully resolve the Yb lattice clock transition. Thus, the linewidth of the probe laser was reduced by stabilizing the frequency to a super-cavity. This was made of ULE with a low thermal expansion coefficient, and was mounted on an active vibration-isolation table at the optimal point for the reduced sensitivity to vibration. Also, this was installed in a vacuum chamber, and the temperature was stabilized to 1 mK level. This system was installed in an acoustic enclosure to block acoustic noise. The finesse of the super-cavity was measured to be 380 000 from the photon life time of the cavity.

이터븀 광격자 시계의 검색 레이저로 쓰기 위하여, WG-PPLN를 사용하여 1319 nm 파장의 Nd:YAG 레이저와 1030 nm 파장의 Yb 도핑된 광섬유 레이저의 합주파수 (578.4 nm)를 발생시켰다. 이터븀 광격자에서 시계 전이선을 분광하기 위해서는 1 Hz 수준의 선폭을 가지는 검색 레이저가 필요하기 때문에, 합주파수로 발생된 노란색 레이저의 주파수를 초공진기에 안정화하여 선폭을 축소하였다. 초공진기는 선팽창 계수가 낮은 ULE로 제작되었고, 진동으로 인한 영향이 작은 받침점에서 능동형 제진대 위에 설치되었다. 공기 굴절률의 영향을 제거하기 위하여 이 초공진기를 진공 체임버 내부에 설치하고, 온도를 1 mK 수준에서 안정화 하였다. 또한, 이 장치들을 방음 체임버 안에 설치하여, 소리로 인한 잡음을 막아 주었다. 실험에 사용된 초공진기의 광자 수명시간으로부터, 그 예리도가 380 000으로 측정되었다.

Keywords

References

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