P/N 201777

4-quadrant laser position sensing detector for CW lasers (using a chopper).

Product family key features

Measure, Track and Align

Follow your laser beam wherever it goes.

4-Channel Detectors

Unique quadrant detector technology senses laser beam position with high resolution.

For CW, Pulsed and High Rep Rate Lasers

  • QUAD-E: energy per pulse from μJ to mJ
  • QUAD-P: powers from μW to mW

From UV to FIR and THz

Absorbers to cover all sources, from UV to millimeter wavelengths

Large Area Sensors

9 mm and 20 mm square detectors

Fast USB 2.0 Connection

Ensures full speed tracking

Includes Application Software

Complete LabView application software included, with many features

Compatible stand

Compatible displays & PC interfaces

Measurement capabilities

  • Noise equivalent power

    2 μW
  • Spectral range

    0.1 - 3000 μm
  • Typical rise time

    0.02 s
  • Typical power sensitivity

    2000 V/W
  • Minimum beam size1

    10 mm Ø
  • Minimum position resolution

    10 μm
  • Maximum chopping frequency

    50 Hz
    • 1. For optimal performance

Damage thresholds

  • Maximum average power density1

    0.1 W/cm²
  • Maximum energy density2

    50 mJ/cm²
    • 1. At 1064 nm.
    • 2. At 1064 nm, 10 ns.

Physical characteristics

  • Aperture width

    20 mm
  • Aperture height

    20 mm
  • Absorber

  • Dimensions

    63.5Ø X 40.6D mm
  • Weight

    0.18 kg


The QUAD-4TRACK is a laser position sensing system designed to support our unique pyroelectric quadrant detectors, QUAD-P and QUAD-E. It is a 4-channel microprocessor-based system that measures the voltage output of each QUAD element and does the math necessary to provide a measurement of the X and Y displacement of a laser beam or image. It is fast and can be used to track, align and/or measure movement in real time, with a resolution of just a few microns!


Our large area pyroelectric quadrant detectors provide unique advantages over other position sensing detectors like silicon quads or lateral effect photodiodes. They are fast, handle high peak power of pulsed lasers without saturation and respond to lasers across the spectrum, from UV to Far IR and even THz. The QUAD-E is intended for use with pulsed sources at up to 1000 Hz, while the QUAD-P is designed for CW and high repetition rate (quasi CW) sources. Both types of detectors can also be used as standalone units, in an analog mode, for incorporation into your own system application. We can provide a lemo pigtail cable for this purpose.


The analog output of the QUAD-4TRACK provides voltage that is directly proportional to the pulse energy or laser power irradiating each QUAD element. When the four voltage outputs are equal, the beam is centered on the QUAD detector. This provides a very useful tool when setting up our QUAD probes with your source for optical alignment.


QUAD-4TRACK includes powerful, stand alone, LabView software which is used to control the instrument, process the data, and display X and Y position. It also displays the energy or power of your source and repetition rate. The large graphic in this screen shows the position of the centroid of the beam and tracks its movement in real time. The software includes many handy features like: set boundary, zoom (2X to 128X), set resolution, data logging, and many more. The green line represents the tracking history.


In the measurement screen shown on the left, we are tracking the beam stability of a pulsed Nd:YLF laser at 10 Hz. The resolution was set at 0.001 nm, the boundary is at 20 µm (red circle), and the zoom feature is at 64X. The total energy is 108.5 µJ, the final position of the laser is at -8 µm in X and -8 µm in Y. The green tracking line shows the movement of the laser about the zero position over a few hundred pulses.


We've developed a unique position calibration routine which allows you to calibrate our QUAD-4TRACK system when working with a uniformly round laser beam. It requires the use of a micrometer-driven linear stage (1-axis only). As you can see from the calibration screen on the left, the procedure involves zeroing the instrument, moving the QUAD probe to nine discrete positions (+2.000 to - 2.000 mm) and then capturing the QUAD readings. It then determines correction coefficients (last column) and applies them to the raw data to arrive at "corrected positions". The QUAD probe is now calibrated!