Nanosecond Fibre Lasers

The wavelength should be chosen around the target material’s absorption, the response of the detector and the compatibility of the complete optical path. The range covers 266, 343 and 355 nm in the UV; 515, 532 and 540 nm in the green region; and 1030, 1064, 1080 and 1550 nm in the near-infrared. UV wavelengths can support fine-feature processing where shorter wavelengths and potentially smaller focused spots are useful, while 1030 to 1080 nm models suit many processing, imaging and LiDAR arrangements. The 1550 nm models are intended for applications including ranging, fibre sensing and optical instrumentation. Wavelength should be fixed before finalising power, coatings, scanners, detectors and laser-safety components.

FL-Nano models are the main choice when average output power and nanosecond timing flexibility are the primary selection criteria. They cover 0.5 to 250 ns pulses, repetition rates generally reaching 1 MHz and average powers up to 30 W. FL-S models use stated peak-power ratings, provide adjustable 5 to 100 ns pulses and extend the repetition-rate range from 1 Hz to 10 MHz. FL-AO models are specified by energy per pulse, with 10 to 100 nJ at 532 nm and nominal 1 to 20 µJ options at 1064 and 1550 nm. The appropriate series therefore depends on whether the design is governed mainly by average power, timing range or pulse energy.

They can support processing where reduced heat diffusion is required, but pulse duration alone does not determine the thermal result. The range provides pulse widths from 0.5 to 250 ns, while available average power extends from milliwatt levels to 30 W. At a fixed average power, reducing repetition rate raises the energy delivered by each pulse, while shortening pulse width raises the approximate peak power for the same pulse energy. Material absorption, focal spot, scanning speed, overlap and heat removal must therefore be considered together. Process trials should be completed using representative materials before defining a production window or claiming cold-processing behaviour.

Many of the 1030, 1064, 1080 and 1550 nm models provide an FC/APC connector or an optional collimated output. A nominal 4 ±1 mm collimated beam is specified for several models, while the higher-power FL-1064-Nano configuration uses a 6 ±1 mm output. Typical fibre lengths are 0.6, 1 or 4 m, depending on the selected version, with PVC jackets and optional metal jackets available for specified configurations. UV and green harmonic models use integrated conversion arrangements and should be treated as complete optical assemblies. Integration planning should also address bend radius, connector cleanliness, back-reflection, beam alignment and the mechanical protection of the delivery path.

Thermal and electrical requirements vary considerably between models, so they should be defined at configuration level rather than for the range as a whole. The specified operating temperature is generally 15 to 35 °C, with air cooling used by many Nano and AO models and conduction cooling used by the compact S series. Water cooling is listed as a range option, although its model allocation is not defined. Electrical versions include 12 VDC/11.5 A, 24 VDC/21 A and 110/220 VAC, with optional 100–240 VAC supplies on selected models. OEM, laboratory and industrial variants may use RS-232, touchscreen or adjustment-knob control, so the enclosure and interface must be selected alongside the optical rating.

Stability depends on the wavelength, output class and selected option. Nano models generally specify RMS power-stability options between <2% and <5%, commonly measured over four hours with an ambient variation of ±3 °C. The S-series options extend to <1% RMS, while AO models state energy-stability options of <2% or <3% RMS. Warm-up time is typically under 15 minutes for Nano and AO configurations and under five minutes for the S series. These figures describe the laser source rather than the complete optical system, so additional drift from mounts, conversion stages, scanners and ambient temperature should be included in the system error budget.

Both fixed and adjustable configurations are available, and the exact behaviour depends on the model. Several UV and green Nano models can be ordered with one fixed pulse width between 0.5 and 50 ns, while adjustable ranges of 0.5 to 5 ns or 5 to 50 ns are also offered. Their repetition rate may similarly be supplied as a fixed value within 0.1 to 1 MHz or as an adjustable range. The 1030 and 1080 nm Nano models cover adjustable pulse widths up to 250 ns, while selected higher-power 532 and 1064 nm versions use defined widths of 4, 8, 14, 20 or 30 ns. The required fixed points and adjustment ranges should be written into the purchase specification.

The exact model suffix, wavelength, output class, pulse width, repetition rate, polarisation, beam delivery, cooling method and control interface should all be confirmed. The FL-1064-AO repetition rate is listed inconsistently as 1–1000 Hz and 1–1000 kHz, so the correct unit and adjustment range require written confirmation. The 1064 and 1550 nm AO configurations also combine a nominal 1–20 µJ range designation with configuration entries of >2 and >20 µJ, making the required pulse-energy class important to document. For UV and green harmonic models, confirm whether pulse width and repetition rate will be fixed at order or user-adjustable. Final acceptance criteria should also cover supply voltage, interlocks, connector type, fibre length and output-beam parameters.