IO-4-1220-VLP

• Designed for 1220 nm laser systems.
• Adjustable narrowband design allows wavelength optimization.
• Tuning range: 1190–1250 nm.
• Operating range: 1180–1260 nm.
• 93% transmission at the center wavelength.
• 38 dB minimum isolation at the center wavelength.
• Ø3.6 mm maximum beam diameter.
• 1.2 W maximum optical power.
• Very Low Power (VLP) polarizer configuration.
• Uses Faraday rotation for non-reciprocal optical isolation.
• Helps suppress back reflections and optical feedback into laser sources.
• Compatible with several Thorlabs mounting adapters, including H1C, SM1B2, and SM087RC/SM087RC/M.
• Suitable for NIR/IR photonics applications requiring polarization-dependent optical isolation.

The Thorlabs IO-4-1220-VLP is an adjustable narrowband free-space optical isolator designed for laser systems operating around 1220 nm.

The isolator uses the Faraday effect to provide non-reciprocal polarization rotation. This allows light to propagate efficiently in the desired forward direction while significantly attenuating light traveling backward toward the laser source. Optical isolators are commonly used to protect lasers from unwanted optical feedback caused by reflections from downstream optics, samples, fiber interfaces, or other components.

The IO-4-1220-VLP is optimized around a 1220 nm center wavelength and provides a tuning range of 1190–1250 nm. Its broader specified operating range is 1180–1260 nm, allowing it to accommodate laser sources that operate near, but not exactly at, 1220 nm.

At the center wavelength, the isolator provides 93% transmission and a minimum isolation of 38 dB. The isolation performance is wavelength-dependent, so maximum isolation is achieved after tuning the isolator for the desired operating wavelength.

The IO-4-1220-VLP is classified as a Very Low Power (VLP) isolator. It supports a maximum beam diameter of 3.6 mm and a maximum optical power of 1.2 W. Thorlabs specifies maximum power densities of 25 W/cm² for blocking and 100 W/cm² for transmission.

The isolator can be integrated into larger optical systems using compatible mounting hardware. Thorlabs lists the H1C, SM1B2, and SM087RC/SM087RC/M as compatible mounting adapters, providing options for FiberBench, SM1 lens tube, or Ø1/2" post mounting configurations.

Product Type: Free-Space Optical Isolator
Part Number: IO-4-1220-VLP
Isolator Type: Adjustable Narrowband
Polarizer Type: Very Low Power (VLP)
Center Wavelength: 1220 nm
Tuning Range: 1190–1250 nm
Operating Range: 1180–1260 nm
Transmission: 93%
Isolation: 38 dB Min.
Maximum Beam Diameter: Ø3.6 mm
Maximum Power: 1.2 W
Maximum Blocking Power Density: 25 W/cm²
Maximum Transmission Power Density: 100 W/cm²
Operating Principle: Faraday Effect
Optical Configuration: Free Space
Polarization: Polarization Dependent
Compatible Mounting Adapters: H1C, SM1B2, SM087RC/SM087RC/M

The transmission and isolation specifications are given at the center wavelength of 1220 nm; actual performance varies with wavelength and tuning. The maximum power specification applies to the combined forward and reverse optical power.

The IO-4-1220-VLP is suitable for a variety of laser and photonics applications, including:

• 1220 nm Laser Systems
• Free-Space Optical Isolation
• Laser Feedback Suppression
• Laser Protection
• NIR Photonics
• Optical Spectroscopy
• Interferometry
• Optical Metrology
• Laser Beam Delivery
• Optical Sensing
• Photoluminescence
• Quantum Optics
• Atomic Physics
• Nonlinear Optics
• Photonics Research
• Scientific Laser Systems
• Fiber-to-Free-Space Optical Systems

The IO-4-1220-VLP is particularly suitable when a 1220 nm free-space laser beam requires protection from back reflections, while maintaining high forward transmission. Its adjustable narrowband design is especially useful when the exact operating wavelength needs to be tuned for maximum isolation.