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Laser Applications | Spectrum

Laser Applications

The unique characteristic of laser light is that it is highly coherent. High spatial coherence means that laser beams can be focused into small spots and collimated beams can travel vast distances with minimal dispersion. Lasers can also produce light that is high in temporal coherence. This means the emitted light has a narrow spectrum or is of a single color. Temporal coherence also makes it possible to produce pulses that are narrow, with the fastest lasers being able to produce pulses that go down into the femtosecond range. The unique quality of laser light has resulted in lasers now being used in an increasing number of applications. This includes fields as diverse as science, medicine, communications, chemistry, printing, data storage, imaging, welding, robotics, surveying, mapping, guidance and cutting.

To convert laser light into an electrical signal a sensor or detector is typically needed. Depending on the application, these sensors can be photo-diodes, photo-multipliers, detectors using scintillation techniques and CCD's,  or some other other photo-voltaic device. For situations that require fast and accurate capture of the electrical signals Spectrum has a range of digitizers that can be employed. For example, 8 bit digitizers are available that offer up to 5 GS/s sampling rates and 1.5 GHz bandwidth. These products are ideal for making timing measurements, or capturing and analyzing pulses, that go down into the nano-second and sub-nanosecond region. When large dynamic range and maximum sensitivity is required high-resolution 14 and 16 bit digitizers are available for the capture and analysis of signals that go as high as 250 MHz in frequency. These high-resolution products deliver outstanding signal-to-noise ratio's (up to 72 dB) and spurious free dynamic range (of up to 90 dB) so that small signal variations can be detected and analyzed.

The digitizers are also equipped with ultra-fast trigger circuits, complete with trigger time stamping, so that the dead-time between acquisitions can be extremely small (down to as little as 16 ns). Together with  large on-board memories (up to 4 Gsamples/card) and advanced streaming and readout modes this makes the digitizers ideal for applications where long and complex signals need to be captured and analyzed. Data can be stored in the on-board memory or streamed in FIFO mode over the fast PCIe bus of the digitizer to a PC. By streaming data to a RAID based storage array it's even possible to seamlessly store hours of information. To help with data analysis and data reduction Spectrum's M4i series of digitizers also feature on-board FPGA based processing functions that can be perform on-the-fly Averaging and Peak detection routines.

Each digitizer card can have from one to four channels and up to eight cards can be linked together with Spectrum's StarHub system to create instruments with up to 32 fully synchronous channels, making them perfect for applications where multiple sensors and large sensor arrays are deployed.

Typical laser applications include laser ranging, 3D modeling, LIDAR and LADAR, LDA/PDA, time interval measurements for printers and optical components, data storage, laser absorption spectroscopy, medical imaging (including optical coherence tomography), mass spectroscopy, interferometry, guidance systems, fiber optic communications, optical backscatter reflectometry and distributed temperature and strain measurement.

Spectrum Product Features

  • 5 GS/s Sampling Rates with high Bandwidth
  • 14 and 16 Bit Resolution
  • Fast Trigger and Read-Out rates
  • On-board Block Statistics (Peak Detect)
  • On-Board Block Average

Matching Card Families

  • M4i.22xx: 8 bit 5 GS/s to 1.25 GS/s digitizer
  • M4i.44xx: 14/16 bit 500 MS/s to 130 MS/s digitizer
  • M2i.59xx: 16 Bit 125 MS/s to 5 MS/s Digitizer

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Useful Links

  • See how a Spectrum M2i.4963-exp digitizer card, programmed under LabVIEW, is used at the Department of Applied Physics and Electronics, Umeå University, Umeå Sweden, in an EC‑QCL (external cavity – quantum cascade laser) system for real‑time breath gas analysis of CO and CO2 by clicking the link here
  • Laser-scanning confocal fluorescence microscopy is a relatively new and important tool for biomedical research. At the University of Tokyo they are able to demonstrate confocal fluorescence microscopy at a record high frame rate of 16,000 frames/s thanks to new research and the use of a Spectrum M4i.2212-x8 high-speed digitizer. Click here to read the full story.
  • By using multi-heterodyne interferometry with a high resolution M4i.4471-x8 digitizer the State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, Tianjin, China, has developed a method for making absolute distance measurements. Experimental results demonstrate an agreement within 750 nm over 80 m distances and an update rate of 167 μs. To see the full white paper click here
  • At the Technical University of Dortmund, Germany, physicists have developed a technique to determine photon correlations of optical light fields in real time. The system uses a high speed Spectrum M4i.2234-x8 digitizer to acquire signals from a balanced homodyne detector. The full details including the experimental setup and results can be found here
  • At the Institute of Geodesy and Photogrammetry, ETH Zürich, Switzerland, a fast Spectrum M4i.2234-x8 digitizer is being used in experiments aimed at solving problems in dimensional metrology. The digitizer is used with ultrashort pulse lasers and spectral manipulation to offer benefits in applications such as long distance measurement and 3D laser scanning. A white paper outlining the experimental approach and results can be found here
  • The Technical University of Dortmund, Germany, is using a M4i.2234-x8 digitizer to sample fast laser signals at 5 GS/s in order to determine photon correlations of optical light fields in real time. The experimental approach and results can be found in the reference paper here with real time light field monitoring of correlation functions being achieved at rates up to 100 kHz.