TwinPDUltra-Low-Noise Balanced Photodetector
for Homodyne Detection
and Precision Laser Stabilization
for Homodyne Detection
and Precision Laser Stabilization
The TwinPD is a compact, ultra-low-noise balanced photodetector designed for high-precision homodyne detection in quantum optics, squeezed-light experiments, and high-speed optical metrology. Its operating principle is based on the direct current subtraction of two individually back-to-back oriented photodiodes, which are socket-mounted to allow easy and user-friendly exchange.
Optimized for shot-noise-limited detection and beyond, the TwinPD combines an outstanding low electronic dark-noise level with a wide signal detection bandwidth for a stable, repeatable performance in both laboratory and industrial environments. The detector features a DC output for convenient photodiode alignment and balance adjustment, an amplified AC output for low-noise signal analysis using spectrum analyzers or data-acquisition systems, and an additional RF output for extracting modulation signals in the MHz range — all integrated into a compact, integration-friendly design.
Lowest Noise – Exceptional Dark Noise Clearance
The TwinPD detector features a carefully optimized electronic design delivering:
- Ultra-low noise performance
- Stable long-term operation
- Maximum sensitivity even for extremely weak optical signals
The gain and bandwidth of each output can be individually customized to optimize sensitivity and dynamic range for your specific application. For optimal squeezing detection at MHz frequencies, we offer, for example, a configuration achieving a clearance of up to 30 dB between shot noise and electronic dark noise at a photocurrent of 30 mA. In addition, we provide custom designs for ultra-low-noise detectors operating in the (sub-)audio frequency range, as well as high-speed detectors with bandwidths of up to 200 MHz.
This makes the balanced detector ideal for:
- Homodyne and differential detection, e.g. for squeezing experiments
- Precision laser measurements at or beyond the quantum noise limit
- High-performance photonics
- Quantum and classical optical experiments
- Balanced interferometry
- Fiber-based laser frequency stabilization
Unmatched Flexibility with Socketed Photodiodes
A key feature of the TwinPD detector is its socketed photodiodes, allowing fast and tool-free exchange. This enables precise optimization for your application in terms
- Photodiode materials: Si, InGaAs, extended InGaAs Ge (others on request)
- Quantum efficiency
- Target wavelength range
The TwinPD’s modular architecture is designed for maximum flexibility and long-term investment protection, seamlessly accommodating evolving system requirements without redesign. Its unique plug-in photodiode concept enables effortless integration of state-of-the-art, highest–quantum-efficiency sensors — including user-selected devices — providing a level of performance scalability and future readiness that sets the TwinPD apart from conventional balanced photodetectors.
Configurable for Any Wavelength
From visible to near-infrared and beyond, the TwinPD detector can be configured for any wavelength upon customer request. This makes it ideally suited for research and industrial environments where spectral flexibility is essential.
Typical use cases include:
- 532 nm / 780 nm / 850 nm applications (Si-sensors)
- 1064 nm / 1550 nm squeezing experiments (InGaAs-sensors)
- 1310 nm and 1550 nm fiber-based systems (InGaAs-sensors)
- Specialized wavelengths (e.g. 2µm) and other waver materials (e.g. Ge, extended InGaAs) are available on request.
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Multiple Individual Outputs for Diagnostics and Data Acquisition
To simplify system integration, alignment, and diagnostics, the detector provides multiple dedicated output channels, such as:
- DC-coupled differential output
- Amplified AC-coupled output for data acquisition
- Additional RF-output for down-stream RF-demodulation (stabilization setups)
The output configuration, such as amplification and corner frequencies for example, can be customized and optimally adapted to your experimental requirements.
Compact and Integration-Friendly Design
Despite its exceptional performance, the TwinPD boasts a compact footprint, allowing seamless integration into space-constrained optical setups and experimental platforms. With housing dimensions of just 87 × 76 × 27 mm³, it enables low beam-height configurations — such as 50 mm — while alternative pedestal mounts make other beam heights easily achievable.
Tailored to Your Requirements
Every experiment is different – your application defines the specification! Custom requests regarding sensitivity, bandwidth, and overall configuration are highly welcome. We work closely with you to deliver a balanced photodetector precisely matched to your needs.
Experience homodyne detection at the highest level — with a balanced photodetector especially designed for your experiment, not the other way around.
For further information, measurements, and quotes, please get in touch: