Changchun New Industries Optoelectronics Technology Co., Ltd.
Lasers, Optics & Photonics

Spectrum Analysis
Laser Application Systems
Laser Measurement & Safety
Laser Marking
Laboratory Instruments
Optics & Coatings
Components & Accessories
Fiber-Coupled LEDs
Customized Products
Laser Measurement & Safety
Power & Stability Measurement
Wavelength Measurement
Pulse Measurement
Longitudinal Mode Measurement
Coherence Length Measurement
Noise Measurement
Polarization State Measurement
Infrared Laser Display Card
Laser Goggles

Customer Service

TTL or Analog Modulation
Fiber Coupling
Coating Service
Laser Marking Service
Complete Solution
Contact CNI
Tel: +86-431-85603799 / 89216078
Fax:    +86-431-89216068

国内: 0431-87020257 / 89216068


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
FPSI 200-532 532-633 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 0-200V 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



Addr: No.888 Jinhu Road High-tech Zone,Changchun 130103, P.R.China 

International Tel: +86-431-85603799  Domestic Tel:  0431-87020257  Fax:+86-431-89216068