Today the fast growing range of new advanced applications require ultra-short pulse durations in the 10-11 to 10-13 s range. Lasers, operating in the picosecond to femtosecond range of pulse durations, also known as ultrafast lasers, are usually produced by chirped pulse amplification technique. IPG pico and femtosecond fiber lasers, based on a master oscillator/ fiber power amplifier (MOFPA) architecture,
are particularly well suited for generation of ultrafast pulses in the range of repetition rates from 10 kHz to several MHz with pulse energies in the range from several microjoules to ~1 mJ. Nonlinear harmonic extensions allow generation of VIS and UV pulses. Such specifications are ideal for micromachining and many other applications.
Ultrafast lasers have become increasingly popular in the recent years in many areas of research, medical procedures and in micro-machining/micro-materials processing. For the purpose of interaction with material, the definition of “ultrafast” usually refers to non-thermal regime of energy absorption. The non-thermal absorption regime is important because it leads to reduced thermal damage in material, allowing smaller features, better control and more precise micro-processing.
With the use of ultrafast lasers, two major mechanisms are primarily responsible for shifting the absorption from thermal to non-thermal regime:
1) Very high instantaneous peak power (in multiple MWatt range) results in simultaneous absorption of several photons, equivalent in energy to
absorption of a visible or UV photon. Comparing with IR lasers, absorption of shorter wavelength UV pulses has long been known to be less thermal even in ns regime, leading to cold ablation rather than melting and vaporization of material. Ultrafast pico and femto pulse lasers can achieve comparable results with IR or green light, eliminating the need to generate UV light.
2) Pulse duration becomes shorter than characteristic time of vibrational relaxation in material. When the energy is deposited faster than it is dissipated through material away from the impact spot, the cold multi-photon absorption becomes more effective, and the heat dissipation is reduced. Opposite to nanosecond lasers, in this regime an increasing pulse energy leads to a higher throughput (higher rate of material removal) rather than additional heating of material.
Continuing miniaturization trend in electronics/semiconductor industries requires smaller and smaller features to be machined with high repeatability, accuracy, precision and throughput on ever longer list of materials. This fuels increasing demand for ultrafast lasers, giving them advantage over nanosecond pulsed lasers despite their higher $/Watt cost. However, until the introduction of IPG line of ultrafast lasers, there has been much room for improvement in the complexity of their design, ease of use, flexibility, package size, robustness and reliability.
Taking advantage of IPG’s well-established expertise in pulsed fiber laser technology, IPG Photonics has developed a series of ultrafast fiber lasers designed for precision micro-materials processing. IPG’s fiber laser pump sources and fiber laser components utilize the intrinsic advantages of fiber laser technology allowing the most robust and cost effective laser tools optimized for industrial use. This range of lasers is expected to significantly increase the use of ultra-short pulse laser micro-machining throughout the industry by eliminating cost barriers to ownership and improving reliability.
In the ultra-short pulse laser processing regime minimal thermal damage to the surrounding non-machined areas can be achieved at efficient material removal rate by employing lasers with a combination of the following features:
increased fluence (W/cm2) by using shorter pulses with higher peak power
increased fluence by using a more focusable (lower M2) beam
improved beam quality and absorption by using a shorter wavelength
increased pulse energy or pulse repetition rate; this will increase throughput as both increase the average power of the laser
improved pointing stability for consistent processing
Both optical parameters and process speed must be carefully tuned to
optimize a particular micro-processing task. If this is not the case, the expected high quality results and/or throughput will not be obtained.
Because of developments by IPG in all of the above, our lasers and systems can process material cost-effectively with minimal thermal damage and with rapid throughput. IPG pico and femto pulse fiber laser models cover the widest range of products across all wavelengths, power levels and pulse durations.
Selecting a laser for a commercial micromaterials processing application is a trade-off among several objectives:
acceptable job quality
minimal equipment cost and cost of ownership
If several lasers differing in wavelength, average power and pulse duration can provide comparable acceptable machining quality, 1 micron laser with the longest pulse duration and the higher average power will typically be preferred, as it will allow the highest throughput at the lowest cost. However, specific material/process may require green or UV femtosecond laser. Erbium or thulium ultrafast lasers may also be preferred when water or some non-metal/polymer absorption profile is at play.
Most often, when a process is developed or transitioned to industrial setting, several lasers are tried to determine the optimal laser and the settings of this laser for the application. IPG Photonics Applications Labs are located around the world and are equipped with micromachining processing stations fitted with various types of nanosecond and ultrafast lasers. Our experienced team of application engineers is ready to assist you in validating your application.
IPG Photonics offers pulsed lasers at various wavelengths from UV to Mid-IR, allowing users to address many different types of materials. Infrared pulsed fiber lasers are available at 1, 1.5 and 2 µm. Non-linear external conversion produces green and 355 nm nanosecond output.
Picosecond and femtosecond pulsed lasers are available in infrared up to 10 W at 1.5 μm, up to 100 W at 1.06 μm or as a second harmonic source up to 5 W at 0.52 μm. Femto pulse lasers range from 400 to 600 fs, pico pulse models range from 10 ps to 1 ns. For some models the pulse duration can be adjusted by the user. Repetition rates range from 10 kHz to 3 MHz. Please contact your IPG Representative for details.
In addition to these fiber pulsed lasers, IPG also provides hybrid fiber-to-crystal pico and femtosecond pulsed Mid-IR lasers: