Thorlabs PM121 400nM Laser Optical Power Meter

The Thorlabs PM121 is a handheld optical power meter engineered for precise measurement of laser and light source power in the visible and near-infrared spectrum. Built around a silicon photodiode detector, it delivers accurate power readings across 400 nm to 1100 nm with sub-10 nW resolution and ±3% calibration uncertainty. The instrument combines a compact 183 mm × 109 mm × 40 mm form factor with USB 2.0 connectivity and LiPo battery operation, making it suitable for laboratory and field deployment.

– Technical Specifications

• Detector: Silicon photodiode
• Wavelength Range: 400 nm – 1100 nm
• Optical Power Range: 500 nW – 500 mW
• Resolution: <10 nW
• Power Calibration Uncertainty: ±3% (400 nm); ±5% (451 – 1000 nm)
• Aperture Diameter: Ø9.5 mm
• Bit Depth: 16 bit
• Time Constant: 1 – 30 s
• Operating Temperature: 0 °C – 40 °C
• Storage Temperature: −40 °C – 70 °C
• Dimensions: 183 mm × 109 mm × 40 mm
• Weight: 350 g

– Key Features

• Silicon detector optimized for 400 nm laser alignment and characterization
• USB 2.0 interface with integrated LiPo 3.7 V, 2600 mAh battery and charger
• Attached IR viewing target with absorption bands at 400–640 nm and 800–1700 nm for aided sensor alignment
• NIST-traceable calibration data stored in sensor head
• 70 dB dynamic range via universal PM120 series console
• Mounting provisions: 1/4"–20, 8–32, and M4 combined tap

– Typical Applications

• UV and visible laser power verification
• Optical system alignment and optimization
• Photodiode sensor characterization
• Field and benchtop measurement campaigns

– Compatibility & Integration

The PM121 integrates with the PM120 series universal console and accepts all S100 and S200 series photodiode-based sensors. Sensor heads support FC, SMA, and SC fiber adapters (e.g., S120-FC, S120-SMA, S120-SC), enabling flexible configuration for diverse optical geometries.