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Optical Receiver, 320-1000 nm Silicon Detector, 125 MHz Bandwidth
Optical Receiver, 320-1000 nm Silicon Detector, 25 kHz - 125 MHz Bandwidth
In Stock
In Stock
Optical Receiver, 900-1700 nm InGaAs Detector, 125 MHz Bandwidth
Optical Receiver, 900-1700 nm InGaAs Detector, 25 kHz - 125 MHz Bandwidth
4 Weeks
4 Weeks



High Speed Receiver Physics

With the advancement of high-transmission-rate systems and short-pulse lasers, many applications now require high time-resolution or equivalently, high frequency-bandwidth optical detection. High-speed photoreceivers are critical for the measurement of the frequency and/or time response of optical systems. In the optical domain, this can include measuring the pulses of mode-locked laser systems, detecting the data stream of a frequency-multiplexed communication system, or providing increased resolution in dynamic, pump-probe spectroscopy. The minimum rise time for high-speed photoreceivers is less than 10 ps. Consequently, for optical signals with faster responses, optical gating techniques are required. In the frequency domain, applications for high-speed photoreceivers include laser heterodyning experiments and millimeter-wave signal generation. The maximum frequency bandwidths for such detectors can exceed 50 GHz in well-designed devices.

Based on the discussion above, diffusion of carriers to the depletion region is a relatively slow process in reverse biased p-n junctions that could serve to limit the response time of a photoreceiver. To minimize this effect, a p-i-n photodiode is typically utilized where an un-doped intrinsic layer is sandwiched between the p and n layers in a p-n junction (see above figure). This structure effectively widens the depletion layer. This results in a greater proportion of the generated current being carried by the faster drift process instead of diffusion. The increased depletion width also allows for a reduction in the RC time constant(via a decreased junction capacitance) and increased area for capturing light. The p-i-n device structure is ubiquitous in high-speed photoreceivers and enables fast rise times and large bandwidths. However, the final measured optical signal will be as slow as the slowest component of a detection system even if a sufficiently fast photoreceiver is employed. Therefore, care should be taken when choosing connectors, cables, an oscilloscope, and a spectrum analyzer to measure a fast optical signal.

Silicon or InGaAs Versions

Silicon models provide visible wavelength coverage from 320-1000 nm and use a silicon-PIN photodiode with a high-gain, low-noise transimpedance amplifier. The near-IR version uses an InGaAs-PIN photodetector that provides coverage from 900-1700 nm.

Typical responsivity of Model 1801 (Silicon) and Model 1811 (InGaAs) detectors.

High Transimpedance Gain and Low Noise

Because of their high transimpedance gain and low noise-equivalent power (NEP), they offer the best in sensitivity for signals with rise and fall times as short as 3 ns. This high sensitivity, combined with their high-level output, reduces the effects of downstream noise sources.

Typical noise floor for Models 1801 (blue) and 1811 (black).

DC Coupled Versions

With true DC coupling, these photoreceivers give linear responses to transient signals without artificial ringing, tails, or other anomalies.

AC Coupled Versions

AC-coupled versions with a low-frequency roll-off at 25 kHz are available. These photoreceivers are useful for measuring a small AC signal on a large cw component. To make alignment easier, AC-coupled versions are equipped with a DC photocurrent monitor output. The monitor output has a 50-kHz bandwidth and a gain of 1 V/mA.

RF Shielding

Careful RF shielding and filtering of power-supply inputs eliminate electromagnetic interference, even in laboratories with Q-switched lasers and other noisy equipment.