Conversion of stability of femtosecond mode-locked laser to optical cavity length

Abstract

In this contribution we propose a scheme for a generation of precise displacements through conversion of relative stability of components of a femtosecond laser into the length of a Fabry-Perot cavity. The spacing of mirrors of a Fabry-Perot interferometer represents a mechanical length standard referenced to stable optical frequency of a femtosecond mode-locked laser. With the help of a highly selective optical filter, it is possible to get only a few discrete spectral components. By tuning and locking the Fabry-Perot cavity to a selected single component it is possible to get a mechanical length standard with the uncertainty of the repetition frequency of the femtosecond laser. To verify the method, an auxiliary single-frequency laser is locked to the resonance mode of the cavity and simultaneously it is optically mixed with an independent optical frequency standard He-Ne-I2. The stability of the beat-frequency between these 2 lasers represents the stability of the Fabry-Perot cavity length. The stability recording evaluated through Allan variances for one hour of operation is presented. The pilot experimental setup is able to generate the length standard in the order of 0.01 nm for 20 min of integration time.

High-resolution detection of small distance changes by an optical frequency comb

“…100 MHz) the detection chain with 1 GHz bandwidth measures beat-note signal well. In this case DFB tunable laser is heterodyned with immediate "tooth" of the comb and the testing range of the optical resonator system becomes to levels of tens of micrometers [14]. Then the testing range is limited only by the range of tuneability of the used tunable laser.…”

“…Then the optical output of the FPC contains number of separated resonance lines [14,15]. Otherwise the optical output from FPC represents the similar signal to the white light continuum and the signal doesn't contain any resonance peaks.…”

Noise Suppression on the Tunable Laser for Precise Cavity Length Displacement Measurement

“…Measurement of the length of etalons and measurement of the length of passive Fabry-Perot cavities [ 1 , 2 , 3 ] or their displacement [ 4 , 5 ] is limited by vibration of mirrors, thermal fluctuations, speed of lock-loops and by the noise and the linewidth of the laser source. The linewidth of the laser should be at least roughly around the linewidth of the passive cavity modes to lock the laser to the cavity by the derivative technique [ 6 , 7 ] or the Pound-Drever-Hall technique [ 8 ].…”

Frequency Noise Suppression of a Single Mode Laser with an Unbalanced Fiber Interferometer for Subnanometer Interferometry

“…Generation of the length of etalons and measurement of the lengths of passive Fabry-Perot cavities [ 1 , 2 ] or their displacement [ 3 , 4 ] is limited by the vibration of mirrors, thermal fluctuations, speed of lock-loops and by noise. Although the linewidth of the laser source is not a limiting factor in the case of a narrow linewidth laser, we should better observe and understand the cavity behavior with a noise-free laser.…”