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Optical Receiver, 320-1000 nm Silicon Detector, 30 kHz to 1 GHz Bandwidth
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Optical Receiver, 900-1700 nm InGaAs Detector, 30 kHz to 1 GHz Bandwidth
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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 wavelength coverage from 320-1000 nm and InGaAs models provide coverage from 900-1700 nm.

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 0.5 ns. This high sensitivity, combined with their high-level output, reduces the effects of downstream noise sources.

Typical frequency response of the 1601-AC (blue) and the 1611-AC (black).

AC Coupled

These photoreceivers are AC-coupled with a low-frequency roll-off at 30 kHz. A convenient DC-photocurrent monitor output makes alignment easy. The monitor output has a 20-kHz bandwidth and a transimpedance gain of 10 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.