Patent Application
20240429673
The present disclosure pertains to the field of mode-locked fiber laser. In particular, the disclosure relates to an intrinsically polarized high energy laser operating in mid-infrared.
With the development of ultrafast optic applications, the importance of mode-locked fiber lasers rapidly increases. In comparison to their solid-state counterparts, the fiber-based nature of such laser oscillators offers a number of advantages due to either a complete absence, or a largely reduced number of free-space intracavity optical elements, in terms of overall stability (for example, mechanical and thermal) resulting in a consequently reduced requirements for external technical maintenance. Moreover, the fiber technology paves a simple way to maintain a linear polarization for the pulse all along the cavity round-trip thanks to widely accessible polarization maintaining fibers and fiber-based components. These features making them a good choice as a seed signal sources for industrial grade energetic ultrafast laser systems. Currently, such mode-locked fiber lasers operating at wavelength below 1.3 μm (especially at 1 μm) are well known to provide a robust operation together with relatively high output energy levels, which offers a certain flexibility and simplifications for the overall system fabrication (reduced numbers of preamplifications stages, spectral and temporal seed pulse properties management). This wavelength limit, imposed by intrinsic properties of silica used in fibers manufacturing, does not allow for high output single pulse energies when the operating wavelengths is longer than silica zero dispersion wavelength (λ>1.3 μm) due to a law of conservation of energy in a form of a well-known soliton area theorem for the energy of a pulse propagating in an anomalous dispersion medium.
Classical approach to overpass this limitation is to up-chirp the intracavity pulse to effectively decrease its peak power, thus making possible to scale up the output energy. In anomalous dispersion regime it is typically done by intracavity dispersion management so that the total dispersion is compensated to reach around null values. Another interesting case, providing up-chirped pulses is, so called, dissipative solitonic regime. Here, the stable pulse propagation is governed not only by nonlinearity and dispersion, but also by a gain and losses of a corresponding medium where pulse propagates. The dissipative soliton regime of operation exists typically when total group delay dispersion (GDD) is higher than null values, which is a natural case for conventional Ytterbium fiber lasers, but demands a stronger dispersion control (typically, total GDD greater than about 0.05 ps2) for laser emitting at wavelength longer than silica zero dispersion wavelength at 1.3 μm.
Usually, the high-energy mode-locked polarized lasers operating in a spectral range where the dispersion of a gain material is anomalous are limited to a wavelength below 1.6 μm, corresponding to the well explored telecommunication range. In this operating range the dissipative soliton pulse propagation regimes are routinely used.
However, wavelength longer than 1.6 μm cannot be obtained with such lasers in a robust way. Indeed, solutions designed to cope with nonlinearity and dispersion rely on intracavity adjustable components which are sensitive to environmental conditions, encountered in industrial area. In particular, bending sensibility and polarization crosstalk becomes hard to control.
Non patent document “All-PM fiber, net normal cavity, Tm-doped fiber laser”, by Aguergaray Claude, Proceedings of SPIE, vol. 9728 Mar. 2016, pages 97280R-1-97280R-7 discloses a passive mode-locked polarized laser operating at 2 μm. This laser has a total GDD value comprised between 4.5 ps2 and 8.3 ps2 associated with a relatively low energy output of 0.36 nJ.
Non patent documents “Dissipative dispersion-managed soliton 2 micron thulium/holmium fiber laser”, by Regina Gumenyuk et Al., Optics Letters, Optical Society of America, vol. 36, no. 5, March 2011, pages 609-611 and “Characteristics of dissipative solitons in an all-fiber thulium-doped fiber ring laser”, by Xia Handing et Al., Optical Engineering, Soc. of Photo-Optical Instrumentation Engineers, vol. 52, no. 5, May 2013, page 54201 also disclose a passive mode-locked polarized laser operating at 2 μm. However, the cavities of these lasers are not polarization maintaining. Moreover, the laser disclosed by Regina Gumenyuk et Al. discloses a polarization controller and does not disclose that each fiber element of the cavity is configured to maintain the polarization generated by the controller. This leads to an unstable energy of the pulses outputting either the cavity when polarization sensitive extra cavity optical elements are applied, or when such a cavity is used as a seed source in a polarized amplification schemes.
It is thus desirable to design high-energy mode-locked polarized lasers operating at wavelength higher than 1.6 μm, typically around 2 μm, and robust/stable enough to be used in industrial environment.
In this disclosure, the total GDD of the cavity is designed to be larger than 0.1 ps2. This feature allows the intracavity pulses to display a spectral bandwidth larger than 3 nm and a large positive chirp in a defined spectral range. Consequently, the amplification capacity of such pulses allows to reach output pulse energy up to 5 uJ after a single amplification stage.
In addition, the cavity is designed to support only one polarization state. It removes the polarization crosstalk between modes with orthogonal polarization, leading to a cavity which is more resistant to external perturbations compared to corresponding not polarization maintaining cavity. This feature can be provided by a fixed state (i.e., not adjustable) polarizer element disposed in the cavity. The combination of both features enables stable high energy pulses operation and is a true benefit at wavelengths where silica-based fibers show anomalous dispersion, preferentially around 2-micron.
characterized in that the operating wavelength is about 2 μm, the net value of the total cavity group delay dispersion (total GDD) is ranging from +0.1 ps2 to +4 ps2 and the cavity is polarization maintaining.
Indeed, the total GDD ranging from +0.1 ps2 to +4 ps2 allows the intracavity pulses to display a spectral bandwidth larger than 3 nm and a large positive chirp in a defined spectral range. Consequently, the amplification capacity of such pulses allows to reach output pulse energy up to 5 μJ after a single amplification stage.
The polarization maintaining cavity allows to remove the polarization crosstalk between modes with orthogonal polarization, leading to a cavity which is more resistant to external perturbations compared to corresponding not polarization maintaining cavity. Besides, avoiding polarization crosstalk limits distribution of energy in several polarized modes leading to unstable output of the cavity, which is not acceptable for industrial application.
According to other advantageous aspects of the invention, the cavity of the passive mode-locked polarized laser comprises:
The combination of the total GDD ranging from +0.1 ps2 to 4 ps2 and the polarization maintaining feature enables stable high energy pulses operation and is a true benefit at wavelengths where silica-based fibers show anomalous dispersion, preferentially around 2 μm.
According to other advantageous aspects of the invention, the passive mode-locked polarized laser further includes one or more of the following features, taken alone or in any possible combination:
In one embodiment, the optical output coupler is coupled to a polarized chirped pulse amplifier temporally and spectrally matched to the oscillator, preferably the polarized chirped pulse amplifier is polarization maintaining.
According to other advantageous aspects of the invention, the polarized chirped pulse amplifier comprises:
According to other advantageous aspects of the invention, the polarized chirped pulse amplifier includes one or more of the following features, taken alone or in any possible combination:
The invention also relates to a method for generating polarized pulsed light having a wavelength of about 2 μm, the method comprising:
According to other advantageous aspects of the invention, the method further includes a step for optimizing a chirp of the oscillator output pulse by adjusting the power of its pump source in a range corresponding to a monopulse mode-lock operating regime.
In the present disclosure, the following terms have the following meanings:
This disclosure relates to a passive mode-locked polarized laser (100, 300, 500).
The passive mode-locked polarized laser (100, 300, 500) comprises an oscillator comprising the following coupled components:
The cavity (101, 301) determines the characteristics of the light pulses output by the oscillator. The light pulses output by the oscillator are ultrashort pulses allowing the energy and peak power of the laser to reach very high values. The ultrashort pulses in this disclosure are characterized by a pulse duration comprised between 0.1 ps and 100 ps. In one embodiment, the ultrashort pulses at the oscillator output are positively chirped and characterized by a chirped and minimally de-chirped (Fourier-limited) pulse durations values comprised between 0.1 ps and 30 ps, preferably between 0.3 ps and 10 ps, more preferably between 0.5 ps and 5 ps.
The total, i.e., over the entire cavity (101, 301), group delay dispersion (GDD), i.e., the measure of the temporal pulse broadening per unit spectral width, must be positive (GDD larger than 0 ps2) leading to the passive mode-locked polarized laser (100, 300, 500) operating in a normal dispersion propagation regime where a longer wavelength component of the output pulse propagates faster than shorter wavelength components making the output pulse positively chirped. The normal dispersion propagation regime allows ultrashort pulses to gain in energy during an intracavity round-trip amplification. In this disclosure, the total GDD is ranging from +0.1 ps2 to +4 ps2. Advantageously, the total GDD is ranging from 0.1 ps2 to 2 ps2.
The pump source (102, 302) is an energy source in a form of photons characterized by a wavelength corresponding to the absorption band of an active medium used in the oscillator cavity (101, 301). In one embodiment, the pump wavelength could be centered on either about 0.79 μm or 1.5 μm.
The optical output coupler (106, 303) allows the extraction of a portion of the light from the cavity (101, 301). In one embodiment, the optical output coupler (106, 303) acts as a spectral filter. The spectral filter may be a chirped fiber Bragg grating (CFBG).
In one embodiment, the optical output coupler (106, 303) is located inside the cavity 301. In one embodiment, the optical output coupler is located outside the cavity 301.
The optical output isolator (104, 304) prevents any external parasitic feedback to the cavity (101, 301) which could perturb the stable modelocking laser operation. In one embodiment, the optical output isolator 304 is located directly after the optical output coupler 303.
In addition, the cavity (101, 301) is polarization maintaining. Preferably, each optical element constituting the cavity (101, 301) is polarization maintaining.
In one embodiment, the cavity (101, 301) comprises:
Preferably, optical pump-signal combiner (107, 307), first reflecting element (106, 306), second reflecting element (105, 305), gain material (108, 308) and dispersion compensation system (106, 309) are polarization maintaining.
The light from a pump source (102, 302) is directed inside the cavity (101, 301) through the optical pump-signal combiner (107, 307). In one embodiment, the optical pump-signal combiner (107, 307) is a cladding pump combiner. In one embodiment, the optical pump-signal combiner (107, 307) is a core pump combiner based on a wavelength division multiplexor comprising a fiber polarizer, a polarization maintaining CFBG, a length of a polarization maintaining anomalous dispersion fiber, i.e., characterized by a negative value of the GDD., and/or a polarization maintaining fiber coupled saturable absorber mirror for dispersion, polarization and repetition rate control. In one embodiment, the optical pump-signal combiner (107, 307) is located between the two reflecting elements (105, 305) and (106, 306). In one embodiment represented in
In one embodiment represented in
In one embodiment, the second reflecting element (105, 305) which is a modelocking reflecting element is a saturable absorber. In one embodiment, the second reflecting element 305 is fiber coupled to a polarization maintaining fiber, the polarization maintaining fiber being then coupled to the optical output coupler 303. In one embodiment, the saturable absorber is a mirror. The mirror may be a carbon nanotube or graphene films deposited directly on a passive fiber facet. In one embodiment the saturable absorber mirror is a semiconductor with maximum modulation depth at about the operating wavelength.
The gain material (108, 308) allows to amplify the energy of signal photons via stimulated emission. The rare-earth elements constituting the gain material (108, 308) define the operating spectral range of the laser. In one embodiment, the gain material (108, 308) is an anomalous dispersion gain material. Preferentially, the gain material (108, 308) is a silica based active fiber. In one embodiment, the active fiber is core-doped with rare-earth elements such as, but not limited to, either purely thulium or holmium ions, or thulium/holmium ions mixture leading to an emission at a central wavelength from an operating spectral range of 1.7 μm to 2.2 μm. In one embodiment, the gain material pumping scheme is optical and could be realized either as cladding, or core-pumped by the optical pump-signal combiner (107, 307). In one embodiment, the energy of the output pulses is comprised between 0.5 nJ and 10 nJ. preferably between 0.5 nJ and 5 nJ, more preferably between 0.5 nJ and 2 nJ.
The dispersion compensation system 309 is a length of material that allows the total GDD over the entire cavity 301 to be normal. In one embodiment, the dispersion compensation system 309 is a fiber with a normal dispersion at about the operating wavelength. The fiber with a normal dispersion may be a fiber with tailored dispersion. In one embodiment, the fiber is a dispersion-shifted (DSF) type fiber or a dispersion-compensating (DCF) type fiber. In one embodiment, the fibered dispersion compensation system 309 is also polarization maintaining. The length of the fibered dispersion compensation system 309 is selected to reach the positive total GDD. In one embodiment, the dispersion compensation is provided by a CFBG. Advantageously, when the CFBG is placed directly after the optical pump-signal combiner 307 in a sense which provides positively chirped pulse after corresponding back-reflection to the cavity, additional length fibered dispersion compensation system 309 does not have to be inserted to reach the positive total GDD value. In one embodiment, the CFBG dispersion has a GDD value higher or equal to 0.5 ps2, preferably higher or equal to 1 ps2. In one embodiment represented in
The fixed, i.e., not adjustable, polarizer (110, 310) allows to polarize the photons without any potential mechanical de-tunings, thus increasing robustness of the device in industrial environment. In one embodiment, the fixed polarizer (110, 310) is a fiber. In one embodiment, the fixed polarizer (110, 310) is a fiber-based in-line linear polarizer.
In one embodiment, the cavity (101, 301) comprises polarization maintaining elements allowing the preservation of the polarization state of the photons all along the cavity. Advantageously, preserving the polarization state all along the cavity avoids random coupling between polarization modes due to a small amount or residual birefringence caused by fibers itself or cavity manufacturing imperfections (including fiber bending, reflective elements integration, etc.). Random coupling between polarization modes leads to a variation of the polarization state in time which is problematic for industrial grade system integration. Polarization maintaining elements introduce strong artificial birefringence leading to random coupling between polarization modes largely reduced. In one embodiment, the polarization maintaining element is a fiber with anomalous or normal dispersion. In one embodiment, the polarization maintaining element is a CFBG. In one embodiment, the polarization maintaining element is an integrated saturable absorber. Preferably, each optical element constituting the cavity (101, 301) is polarization maintaining.
In one embodiment, the cavity (101, 301) further comprises a spectral filtering element to restrict the operating wavelength. The spectral filtering element may be a Bragg grating element with anomalous or normal dispersion polarization maintaining fiber. In one embodiment, the optical output coupler 303 includes the spectral filtering element. In one embodiment, the optical output coupler 303 includes the Bragg grating.
Advantageously, the spectral filtering element has a bandwidth ranging from 5 nm to 60 nm. Here, the bandwidth corresponds to the reflected wavelengths. The combination of such a bandwidth with a total cavity group delay dispersion ranging from +0.1 ps2 to +4 ps2 provides with an oscillator outputting pulses with a spectral bandwidth included in the bandwidth of the spectral filtering element, preferably ranging from 3 nm to 50 nm. The spectral filtering element facilitates the spectrally matching of the oscillator with a chirped pulse amplifier. Moreover, as explained hereafter, the combination of such a spectral bandwidth of the spectral filtering element with such a total cavity group delay dispersion allows ultrashort pulses (with at least several picoseconds duration) to be amplified up to a high peak power (larger than 0.5 MW) and/or high energy (larger than 0.5 μJ) using a chirped pulse amplifier.
In one embodiment, the cavity (101, 301) further comprises a length of passive fiber (111, 311) allowing the control of the repetition rate. In one embodiment, the passive fiber (111, 311) is polarization maintaining. In one embodiment, the passive fiber (111,311) has anomalous dispersion. In one embodiment, the repetition rate of the cavity (101, 301) ranges between 2 MHz and 150 MHz, preferably between 2 MHz and 30 MHz.
In one embodiment represented in
In one embodiment, the polarized chirped pulse amplifier 512 comprises:
The pulse stretcher element 515 allows to stretch the polarized ultrashort pulses output by the oscillator to effectively decrease their peak power. In one embodiment, the pulse stretcher element 515 is a spectral filter. In one embodiment, the pulse stretcher element 515 is a CFBG. In one embodiment, the pulse duration stretching factor ranges between 14 ps/nm and 60 ps/nm leading to a duration of the stretched pulses ranging between 200 ps and 700 ps for a single passage. In one embodiment, considering pulses wavelength of about 2 μm and pulses full width at half maximum spectral bandwidth of about 15 nm, the pulse stretcher element 515 allows to stretch the pulses up to about 350 ps or about 500 ps. In one embodiment, the pulse stretcher element 515 has an adjustable chirp allowing to have an additional degree of freedom for the temporal matching. In one embodiment, the pulses are directed to the pulse stretcher element 515 via a polarization maintaining optical circulator 514.
The advantage of a total GDD lower than 4 ps2 is that this value allows to reach high energies of the amplified pulses. Indeed, when the total GDD increases, the oscillator spectral bandwidth decreases. Since the pulse duration stretching factor is expressed in ps/nm, a narrow spectral range leads to a short duration of the stretched pulses. The longer the duration of the stretched pulses, the higher the linear amplification. Indeed, the threshold of nonlinear effects is effectively pushed up avoiding the influence of detrimental nonlinear effects on a pulse shape. When the total GDD is larger than +4 ps2. the spectral bandwidth of the pulses outputting the cavity becomes too narrow leading to weak stretching of the pulses outputting the oscillator and consequently to lower threshold of nonlinear effects thus limiting the accumulation of the energy in a single pulse. In other words, the combination of the values of the total GDD and values of the pulse duration stretching factor of this disclosure provides optimized chirped pulse amplifier configurations allowing to reach high pulse energies. Advantageously, the total GDD is equal to or lower than 2 ps2: With this value of 2 ps2 for GDD and a pulse spectral bandwidth of 3 nm associated with a stretching factor of 60 ps/nm, pulse energy output after single stage chirped pulse amplifier can reach about 1.5 μJ. With a value lower than 1 ps2 for GDD and a pulse spectral bandwidth of about 10 nm (see
The preamplification stage 517 allows to compensate losses due to the different elements of polarized chirped pulse amplifier 512. In one embodiment, a single preamplification stage 517 allows to partly compensate insertion losses issued from the fibered pulse stretcher element 515 and the pulse picker element 518 due to an already relatively high energy seed signal allowed for the total GDD values range specified above. In one embodiment, the preamplification stage 517 comprises a thulium doped fiber. In one embodiment, the preamplification stage 517 is based on a single mode polarization maintaining active fiber. In one embodiment the output of the preamplification stage is optically isolated with helps of fibered optical isolator to prevent any possible parasitic light feedbacks from following stages.
The main function of a pulse picker element 518 is to decrease a repetition rate of the pulses output by the oscillator to ease an access for high energy output. The repetition rate of the pulse output by the polarized chirped pulse amplifier 512 may be lower than 30 MHz. In one embodiment the repetition rate of the pulse output by the polarized chirped pulse amplifier 512 lies between 200 kHz and 1 MHz leading to the use of a single preamplification stage 517. In one embodiment, the repetition rate of the pulse output by the polarized chirped pulse amplifier 512 lies between 50 kHz and 200 kHz which may lead to the use of an additional preamplification stage to that of 517, preferentially situated immediately after pulse picker element 518. In one embodiment, the fibered pulse picker element 518 is based on a single mode polarization maintaining fiber with anomalous dispersion. In one embodiment, the pulse picker element 518 is an acousto-optic modulator. In one embodiment, the pulse picker element 518 is located after the corresponding preamplification stage 517.
The amplification stage 519 allows to amplify the stretched pulses up to high energies. In one embodiment, the amplification stage 519 is based on a purely single mode thulium fiber. In one embodiment, the fiber of the amplification stage 519 is polarization maintaining. In one embodiment, the at least one amplification stage 519 is based on a large mode area active fiber. In one embodiment, the amplification stage 519 is based on doped bulk material. In one embodiment, the amplification stage 519 is based on a hybrid configuration comprising doped fiber and doped bulk material.
In one embodiment, the polarized chirped pulse amplifier 512 further comprises a pump stripper element 520 dedicated to evacuate not absorbed pump radiation.
The free-space compressor 521 allows to compress the amplified stretched pulses to provide ultrashort and high peak power pulses. The spectral transmission bandwidth of the free-space compressor 521 can be greater than that of the pulse stretcher element 515. Alternatively, the spectral transmission bandwidth of the free-space compressor 521 can match spectrally the pulse stretcher element 515-including eventually a spectral transmission bandwidth of the free-space compressor 521 slightly narrower than that of the pulse stretcher element 515. The lower limit of the spectral transmission bandwidth of the free-space compressor 521 is determined by the spectral clipping effect. Indeed, the spectral transmission bandwidth of the free-space compressor 521 can be narrower than that of the pulse stretcher element 515 as long as the spectral clipping effect perturbing ultrashort compressed pulse shape is not significant. In one embodiment, the free-space compressor 521 comprises at least one chirped volume Bragg grating.
In one embodiment, the energy of the pulses output by the polarized chirped pulse amplifier 512 ranges from 0.5 μJ to 5 μJ after compression related to a single (or first) amplification stage 519, ranges from 1 μJ to 20 μJ after a possible second amplification stage 519 and ranges from 1 μJ to 40 μJ after a possible third amplification stage 519 when a single passage through the pulse stretcher element 515 is considered.
In one embodiment, the pulse duration of the compressed pulses output by the polarized chirped pulse amplifier 512 ranges between 0.1 ps and 30 ps, preferably between 0.3 ps and 10 ps, more preferably between 0.5 ps and 5 ps.
In one embodiment, a length of fiber is used to improve the temporal, dispersion and spectral matching between the pulse stretcher element 515 and free-space compressor 521. In one embodiment, the length of fiber is inserted directly after the optical output coupler 303. In one embodiment, the length of fiber is inserted after the pulse stretcher element 515 and the polarization maintaining optical circulator 514. In one embodiment, the length of fiber is inserted between the pulse stretcher element 515 and the polarization maintaining optical circulator 514. The polarization maintaining optical circulator 514 allows for twofold reducing of the complementary lengths of matching fiber by using back and forth passage of reflective stretcher element.
The disclosure also relates to a method for generating polarized pulsed light having a wavelength of about 2 μm, the method comprising:
In one embodiment, the method further comprises a step for optimizing a chirp of the oscillator output pulse by adjusting the power of its pump source (102, 302) in a range corresponding to a monopulse mode-lock operating regime aiming to finely tune or remove the residual linear chirp of a compressed pulse duration. Optimizing an oscillator means that the oscillator configuration provides a simple and repeatable realization of said oscillator and a simple and repeatable utilization of said oscillator with a chirped pulse amplifier. This optimization is thus crucial for industrial grade systems. Usually, it is not repeatable due to a fact that CFBG and CVBG elements have a large fabrication tolerance. Therefore, for each system the use of a new stretcher and compressor couple requires a complementary fine tuning of the stretched pulse duration for optimal temporal (dispersion) matching.
The present disclosure is further illustrated by the following examples.
Example 1: a passive mode-locked polarized laser wherein the second reflecting surface is the CFBG.
As shown in
This example laser is implemented in industrial conditions and demonstrated the following performances: more than 1000 hours maintenance-free operation (actually 8000 h operation were achieved without maintenance), short warm-up time (lower than 30 min), large pulse to pulse stability (less than 2% RMS over 1000 shots), long-term stability (less than 2% RMS over 8 h) in average climate parameters of 20-28° C. and 50-70% humidity. The spectrum of the pulses output by this example embodiment are represented in
The gain fiber 108 defines the operating wavelength to 1966 nm. The length of polarization maintaining anomalous dispersion passive fiber 111 allows for the total GDD value to be equal to +0.114 ps2 and the repetition rate to be equal to 19.15 MHz. The energy of the output pulses corresponding to monopulse modelocking regime was measured after optical isolator 104 to range between 0.45 nJ and 1.05 nJ. The corresponding pulse duration of the outputting pulses was measured to range between 2 ps and 6 ps after propagation in about 7 m of standard polarization maintaining fibers, measured from the middle of the first reflecting element 106. The corresponding full width at half maximum spectral bandwidth of the pulses measured at −10 dB is varying in the range between 10 nm and 15.5 nm.
Example 2: a passive mode-locked polarized laser wherein the second reflecting surface is a linear mirror.
As shown in
The spectrum of the pulses output by this example embodiment is represented in
The short length of gain fiber 308 and output coupling ratio of 90% mainly defines the operating wavelength to 1955 nm. The total GDD value is +0.18 ps2. The combination of polarization maintaining normal dispersion fiber 309 and 311 also allows the repetition rate to be equal to 14.9 MHz. The maximum energy of the pulses at the output of optical isolator 304 for the oscillator operating in monopulse regime is 1.3 nJ. The duration of the outputting pulses is 29 ps. The corresponding full width at half maximum spectral bandwidth of the pulses measured at −10 dB is 7 nm.
Example 3: a polarized chirped pulse amplifier coupled to the passive mode-locked polarized laser through the optical output coupler.
As shown in
This example embodiment is implemented in industrial conditions and demonstrated the following performances: more than 1000 hours maintenance-free operation, short warm-up time (lower than 30 min), large pulse to pulse stability (less than 2% RMS over 1000 shots), long-term stability (less than 2% RMS over 8 h) with diffraction limited divergence (M2<1.1) and beam pointing stability strong enough to provide successful application in various semiconductor micromachining manufacturing protocols (for example, with ability to three dimensional control of a micrometer scale material modifications inside a silicon) in conditions with average climate parameters of 20-28° C. and 50-70% humidity. The autocorrelation trace of the pulses output by the polarized chirped pulse amplifier 512 is represented in
The pulse picker element 518 reduces the repetition rate to about 200 kHz. The energy of the pulses output by the polarized chirped pulse amplifier is about 1.4 μJ and measured compressed pulse energy of is about 1.1 μJ, slightly limited by insertion losses of compressor stage optics.
| Number | Date | Country | Kind |
|---|---|---|---|
| 21305602.1 | May 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/062393 | 5/9/2022 | WO |
