Optically Pumped Far Infrared Lasers

Edinburgh Photonics, a division of Edinburgh Instruments, has more than three decades of experience in designing and producing a wide range of optically pumped FIR (Terahertz) lasers. The products are utilized in applications that require coherent radiation in the spectral range of 40 µm to 1.22 mm (0.25 -7.5 THz). When used in combination with Edinburgh’s PL Series of CO2 lasers, the FIR laser helps in obtaining laser line measurement at high peak powers.

295 FIR Laser

Edinburgh Photonics has designed a stand-alone FIR laser, model 295, for use with high power CO2 lasers. Definite powers of 150 and 500 mW when pumped by the PL5 and PL6 lasers, respectively, are available at 118.8 and 184.3 µm.

The 295 FIR laser incorporates the same optical design as utilized in the FIRL 100 laser. It includes a 3 bar invar support frame and has been designed to enable UHV pumping for maximum power and extended sealed operation.

395 Twin Laser

The 395 twin laser has been specifically designed for applications that require two FIR outputs, like Plasma diagnostics, with one frequency offset from the other by a few MHz. The twin laser includes two similar FIR laser cavities in a 5 bar invar stabilized frame.

These FIR cavities are pumped by a PL6 laser in order to ensure high stability of the Intermediate Frequency. Also, to produce the required identical pump beams, a 50/50 beam splitter is utilized. Both FIR sections have output couplers that are placed on precision linear translation stages for separate optimization and to produce the cavity length difference for frequency offset.

FIRL 100 Laser

Optically pumped FIR laser.

Figure 1. Optically pumped FIR laser.

The model FIRL100 laser includes both the FIR laser and the CO2 pump laser enclosed in an integrated structure joining an optically pumped FIR system into a compact unit.

To acquire excellent mechanical and thermal mechanical stability, the lasers and coupling optics are placed inside a 5 bar invar rod frame.

The CO2 section includes a flowing gas single discharge tube. Mode performance is ensured using high quality optics and by internal profiling of the tube.

The resonator design is built on the PL5 laser with diffraction grating, a piezo ceramic mounted ZnSe output coupler, and two ZnSe Brewster windows. Through a ZnSe focusing lens and two steering mirrors, the CO2 laser output is joined to the FIR laser. A two position sliding mirror mechanism provides access to the CO2 radiation beam diagnostics to perform Infrared experiments.

FIRL 100 far infrared output specification.

λ(μm) FIR Molecule CO2 pump line Typical Power
96.5 CH3OH 9R10 60mW
118.8 CH3OH 9P36 150mW
184.3 CH2F2 9R32 150mW
432.6 HCOOH 9R20 30mW
513.0 HCOOH 9R28 10mW

FIR laser frequencies tend to originate from rotational transitions in an excited vibrational state of a polar gas molecule at reduced pressure.

The FIR laser depends on the selective absorption of tunable infrared radiation to generate a population inversion between rotational states, and thus produce laser action.

Accessories for FIR Series

For the FIR laser series, a variety of accessories are available, such as Laser stabilizers, gas mixing stations, and laser pumping and refilling systems. Edinburgh Photonics has developed a range of active stabilization methods to suit the type of laser and operating conditions.

Power Supplies Based on Resonant Inverter Technology

Standard high voltage DC excitation is utilized to excite the laser discharge. Each laser is powered by one of the LPS series of switch mode power supplies, which are built on resonant inverter technology to ensure high efficiency and reliability.

The LPS range is available with CW or chopped operation up to 1 kHz. The PL5 laser can also be powered with the PS4P valve controlled power supply delivering programmable chopped, CW and pulsed operation. Stabilizers, coolers, gas handling systems, and other accessories are available for each laser.


A wide range of optically pumped FIR lasers are available for applications requiring coherent radiation in the spectral range of 40 µm to 1.22 mm (0.25 -7.5 THz). Depending on the model of the CO2 pump laser used, output powers of 150 and 500 mW at the 118.8 p,m and 184.3 micron methanol (CH3OH) lines can be ensured. The FIR lasers are Invar bar stabilized and come with single or dual output.

This information has been sourced, reviewed and adapted from materials provided by Edinburgh Instruments.

For more information on this source, please visit Edinburgh Instruments.


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