- Heterodyne Detection
- Optical Coherence Tomography
- Optical Delay Measurements
- THz Detection
- Large Active Areas for Free-Space Beams
- Three Models
- 190 - 1100 nm (UV Enhanced Al)
- 320 - 1060 nm (Si)
- 800 - 1700 nm (InGaAs)
- Excellent Common Mode Rejection
- High Bandwidth: DC to 1 MHz
- Ultra Low Noise
- Detector Types: Si or InGaAs
- Designed for Free-Space Applications (Fiber Input Also Feasible)
- Direct Detector Monitor Outputs
- Switchable Power Supply Included
- External SM1 Threads and Internal SM05 Threads
These Balanced Amplified Photodetectors utilize two well-matched large-area Si or InGaAs detectors and an ultra-low noise transimpedance amplifier to detect signal path differences in two beams. An output voltage (RF-OUTPUT) is generated that is proportional to the difference between the photocurrents in the two photodiodes (i.e., the two optical input signals). Additionally, the unit has two fast monitor outputs (MONITOR+ and MONITOR-) to measure optical input power levels as well as RF modulated signals on each detector.
The detectors are spaced 2" apart, making beam alignment an easy task on an optical table. To further simplify the use of these detectors, the housing has external SM1 (1.035"-40) and internal SM05 (0.535"-40) threads around each detector to attach components such as lens tubes, cage systems, mounted optics, and fiber adapters.
The PDB200 Balanced Detector Series act as a balanced receiver by subtracting the two optical input signals from each other resulting in the cancellation of common mode noise. This allows small changes on the signal path to be extracted from the interfering noise floor.
These balanced amplified photodetectors are comprised from two balanced photodetectors and an ultra-low-noise transimpedance amplifier. The intelligent design of these devices allow an improved matching of the two balanced photo detectors to achieve an excellent common mode rejection, leading to better noise reduction. Please see the Operation Tab for more details.
The optical signal inputs are free space for the PDB200 Series, but the items do feature external SM1 (1.035"-40), and internal SM05 (0.535"-40) threads for fiber adapter mounting. This allows easy adaptation to either fiber coupled or free space applications. Three electrical BNC connectors provide the balanced output signal plus a power monitor for each of the two input signals. These two monitors enable the control of the input power levels and can be used as an independent power meter for each channel.
The PDB200 Series is housed in a rugged, shielded aluminum enclosure. The housing allows a mounting post adapter to be fixed to the bottom or side surface by 8-32 (M4) screws. The unit is powered from a ±12 V DC power supply which is provided with the unit. The input voltage of 110 V or 230 V can be manually selected by a switch.
Thorlabs also offers Fiber-Based Interferometers, which feature an integrated balanced detector.