Photodiode Sensors

Coherent Photodiode Sensor

Ideal for measuring the power from low power CW lasers

Further Information
» Photodiode Sensor Datasheet

Coherent’s LM-2 & OP-2 photodiode sensors are designed for low power measurements in the range from 1nW to 50mW (5W with optional attenuator) in the 250 ... 1550nm band.

Photodiodes offer high sensitivity and low noise, enabling them to detect very low light levels. However, they saturate above approximately 1mW/cm², so attenuating filters must be used when operating at higher powers, such as the Coherent 1000:1 accessory filter. Photodiodes also have a fast response time, so they can be convenient for tuning and peaking lasers. Photodiodes have a much more limited spectral range and lower spatial uniformity than thermal sensors. The latter can affect the measurement repeatability of non-uniform beams or of beams that wander over the detector surface between measurements. Photodiode sensors are not designed for use with pulsed lasers. Coherent photodiode sensors are calibrated using a monochromator for use over their full specified wavelength range.

The OP-2 sensors are directly compatible with the Coherent FieldMate, FieldMax II TO / TOP and LabMax TO / TOP laser power meters. The LM-2 sensors must be used in conjunction with the accessory SmartSensor adaptor. The OP-2 VIS sensor is available with selected meters at reduced prices as part of Coherent's power meter value package programme. For testing the power from optical fibres or fibre-coupled lasers, accessory fibre optic adaptors are available that screw onto the photodiode sensor heads.

Specifications & Ordering Information

Model	Type	Wavelength Range	Uncertainty	Max. Power	Min. Power	Resolution	With Attenuator	Detector Dia.
OP-2 UV	Silicon	250 - 400nm	+/- 8%	30mW	10nW	1.00nW	N/A	6.0mm
OP-2 VIS	Silicon	400 - 1064nm	+/- 5%	50mW	10nW	1.00nW	5W	7.9mm
OP-2 IR	Germanium	800 - 1550nm	+/- 4.5%	10mW	10nW	1.00nW	1W	5.0mm
LM-2 UV	Silicon	250 - 400nm	+/- 8%	30mW	10nW	1.00nW	N/A	6.0mm
LM-2 VIS	Silicon	400 - 1064nm	+/- 5%	50mW	10nW	1.00nW	5W	7.9mm
LM-2 IR	Germanium	800 - 1550nm	+/- 4.5%	10mW	10nW	1.00nW	1W	5.0mm
Accessories
33-1298	1000:1 optical attenuator for photodiode sensors¹
33-1413	Fibre optic adaptor, SMA
33-1421	Fibre optic adaptor, DIN 2106
33-1439	Fibre optic adaptor, FC/PC
1056827	SmartSensor adaptor²

(1) 1000:1 attenuator provides attenuation between 1100:1 and 950:1, depending upon the laser wavelength. Useful
     working range is 400-1800nm. Suitable for use at upto 100MW/cm². Calibrated at 647nm with an uncertainty
     of +/- 5%.
(2) The SmartSensor adaptor allows Coherent LM-2 series photodiode sensors to be used with FieldMax II TO,
     FieldMax II TOP and FieldMate power meters.