2000nm 3-Port High Power PM Optical Circulator: Applications and Selection Guide

2026-10-08

The 2 μm wavelength band has moved from research labs into real products. Thulium- and holmium-doped fiber lasers operating around 1900–2100 nm now power surgical tools, polymer welding stations, eye-safe LiDAR and gas-sensing instruments. As these systems grow more powerful and more polarization-sensitive, the components that route light through them must keep pace. One of the most important is the 2000nm 3-port high power PM optical circulator.

This guide explains what the device does, where it is used, and which specifications matter most when selecting one.

What Is a 2000nm 3-Port High Power PM Optical Circulator?

An optical circulator is a non-reciprocal device that directs light in a fixed sequence of ports. In a three-port design, light entering Port 1 exits Port 2, and light returning into Port 2 exits Port 3. It cannot travel backwards from Port 2 to Port 1.

A polarization maintaining (PM) circulator does this while preserving the polarization state of the light, using PM fiber pigtails and a precisely aligned internal optical path. If you would like a refresher on the underlying physics, our article on the operational principle of a polarization maintaining optical circulator covers it in detail.

The 2000nm high power version adds two things on top of this:

• Materials and coatings optimized for the 2 μm band, where standard 1550 nm components suffer from high absorption and poor isolation.
• Higher power handling, so the device can sit in amplifier chains and laser cavities rather than only in low-power test paths.

Models with a fast axis blocked configuration pass light only along the slow axis of the PM fiber. This acts as a built-in polarization filter and helps maintain a high extinction ratio across the system.

Why Circulators at 2 μm Are Harder to Build

Designing a 2μm three-port polarization maintaining circulator is not simply a matter of scaling a 1550 nm design. Faraday rotator materials have different Verdet constants at longer wavelengths, which changes the length and magnetic field required for a 45° rotation. Absorption in optical materials also rises, which converts more light into heat at high power.

Heat is the enemy of isolation and polarization stability. That is why thermal design, which we discussed in thermal stability in 2.0μm polarization maintaining optical isolators, is equally critical for circulators in this band.

Key Applications

1. Thulium fiber laser and amplifier design
   In master oscillator power amplifier (MOPA) setups, a circulator can separate forward and backward-travelling light, allowing engineers to monitor reflections or build double-pass amplifier stages that extract more gain from the fiber.
2. Medical and surgical lasers
   Water absorbs strongly near 1940 nm, making 2 μm lasers effective for precise tissue cutting and ablation. A high power 2000nm PM fiber circulator helps route returning light safely and protects the source from back-reflections off tissue or delivery optics.
3. Eye-safe LiDAR and free-space sensing
   Wavelengths above 1.4 μm are considered eye-safe at much higher power levels. In coherent LiDAR, a single aperture often sends and receives light, and the circulator separates the outgoing beam from the returning signal.
4. Gas and environmental sensing
   Gases such as CO₂ and water vapour have strong absorption lines near 2 μm. Circulators enable reflective sensing architectures, including setups with fiber Bragg gratings and Faraday mirrors.
5. Pumping mid-infrared sources
   2 μm lasers are often used to pump holmium lasers or optical parametric oscillators that reach further into the mid-infrared, where polarization stability directly affects conversion efficiency.

Specifications to Check Before You Buy

When comparing a 2000nm PM fiber circulator for your system, focus on these parameters:

• Operating wavelength range: Confirm the centre wavelength and bandwidth match your laser line (for example, 1950 nm or 2050 nm).
• Insertion loss: Lower loss preserves power and reduces heat. See our guide on minimizing insertion loss in a polarization maintaining optical circulator.
• Isolation: Determines how well the device blocks unwanted reverse paths.
• Extinction ratio: Indicates how well the output polarization is preserved.
• Power handling: Check both CW and peak power ratings, especially for pulsed systems.
• Fiber type and connectors: Ensure the PM fiber matches the rest of your 2 μm setup to avoid splice loss and polarization misalignment.

Building a Complete 2 μm PM System

A circulator rarely works alone. Most 2 μm systems also use a 2.0μm polarization maintaining optical isolator to protect the seed laser and a 2.0μm single-mode fused coupler for power tapping and monitoring. For systems at other wavelengths, DK Photonics also offers a full range of polarization maintaining optical circulators.

Conclusion

As thulium and holmium fiber lasers push into higher powers and more demanding applications, component choice has a direct impact on performance and reliability. A well-designed 2000nm 3-port high power PM optical circulator keeps light moving in the right direction, preserves polarization and survives the thermal load of real-world operation.

Explore the DK Photonics 2000nm 3-port high power PM optical circulator to find the right configuration for your 2 μm system, or contact our team for a custom specification.

Frequently Asked Questions

1. What is a 2000nm 3-port high power PM optical circulator used for?
   It routes light from Port 1 to Port 2 and from Port 2 to Port 3 while preserving polarization at 2 μm wavelengths. It is used in thulium fiber lasers, medical lasers, eye-safe LiDAR, gas sensing and mid-infrared pump systems.
2. What does “fast axis blocked” mean in a PM circulator?
   It means the circulator only transmits light aligned to the slow axis of the PM fiber and blocks light on the fast axis. This improves the polarization extinction ratio of the system.
3. Can I use a 1550nm circulator in a 2 μm laser system?
   No. Materials, coatings and Faraday rotators in 1550 nm circulators are not optimized for 2 μm, which leads to high loss, poor isolation and heating. A circulator designed for the 2000nm band should be used.
4. Which specifications matter most when choosing a 2μm PM circulator?
   The key specifications are operating wavelength, insertion loss, isolation, extinction ratio, power handling and fiber type. Power handling is especially important in amplifier and pulsed laser applications.
5. Why are 2 μm lasers used in medical applications?
   Water absorbs strongly near 1940 nm, so 2 μm lasers deliver energy into a very thin layer of tissue. This allows precise cutting and ablation with limited thermal damage to surrounding tissue.