Changchun New Industries Optoelectronics Technology Co., Ltd.
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Tel: +86-431-85603799 / 89216078
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Longitudinal Mode Measurement——Scanning F-P Interferometer

     Laser longitudinal mode refers to the axial distribution of the light field along to its direction of propagation. An ordinary laser usually has a few or dozens of longitudinal modes. Using high resolution spectrometer to test the laser spectrum, there will be multiple laser frequencies (or wavelengths). If restraining most of the longitudinal modes through selecting frequencies and just retaining one of them, then we could get single longitudinal mode (single frequency) laser.Single longitudinal laser compares with ordinary laser, has narrower line width and coherence length. It is widely used in spectrum analysis, holographic imaging, interferometry and other fields.
     Scanning Fabry-Perot interferometer is a kind of spectrum analyzer, which is suitable for detecting the subtle spectral characteristics of continuous lasers. It mainly includes sawtooth signal generator, Fabry-Perot interference cavity, and high-speed photodetector.

Testing Instrument: Scanning F-P Interferometer

  • Confocal Fabry-Perot Design

  • The reflectance of the lens remains above 99% in the range of 532-633 nm

  • Photodiode Detector Included

  • Free Spectral Range: 2.5 GHz

  • Minimum Finesse: 200


Model Wavelength Range Free Spectral Range Total Finesse Resolution Cavity Length Mirror Substrate
FPS1200-532 532-633 nm

(Other wavelengths can be customized)
2.5GHz ≥200 <12.5 MHz 30 mm UV Fused Silica

Scanning F-P Controller Box


  • Sawtooth Scan Voltage

  • For Piezoelectric Transducer

  • Scan the Separation between the Two Cavity Mirrors

  • High voltage signal duty cycle and amplitude adjustment range are adjustable.

Oscillogram Output Voltage Range Frequency Conversion
Sawtooth 0-10V 0.05/ 0.1/ 0.5/ 1/5 s

Examples of Testing Results

Single longitudinal mode testing Multiple longitudinal modes testing

Single longitudinal mode testing

Multiple longitudinal modes testing



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