When the module is switched to selflocking mode, users can turn onoff the connected appliance immediately there are two wiring way. At the same time, highpower pulses of such a duration can easily be formed in the qswitched regime with longitudinal mode selection 7, 8. Our full family of dental composite products will meet all your bonding needs. Kerr lens mode locking klm is another technique that can be realized in a simple cavity without the need of an auxiliary cavity. The presence of a lenslike e ect inside the crystal, similar to thermal lensing. This clear lens can be used in all kerr lighting 4 x 8 residential fixtures with gray colored base. As the kerr lens induced in the nonlinear medium strongly depends on the resonator internal power, we have measured the output power in mode locked operation as a function of output coupling see fig. Kerrlens modelocked klm bulk lasers are very attractive for the generation of ultrashort pulses for numerous applica tions in frequency. The optical kerr effect causes a refractive index intensity. Kerr lens mode locking without nonlinear astigmatism.
The generation of 72fs hyperbolic secant pulses centered at 1050nm with 17. So far, all femtosecond thindisk oscillators have been mode locked by means of sesam. Initiation of the self mode locking took place through the use of liquid saturable absorbers to establish saturation parameters, and it was carried out in optimized allsolidstate laser configurations but with gaslaser. The kerr effect, also called the quadratic electrooptic qeo effect, is a change in the refractive index of a material in response to an applied electric field. Pulses as short as 85 fs at a central wavelength of 1074. Pdf feasibility of kerrlens mode locking in fiber lasers. For negative n 2, the nonlinearity is selfdefocusing. Analysis of laser cavities with selfstarting kerrlens mode. Thesis submitted to the senate of barilan university. In addition the position of a hard or soft aperture similar as a fast saturable absorber in a klm laser is discussed. Multipulse operation and limits of the kerrlens mode. The kerr effect is distinct from the pockels effect in that the induced index change is directly proportional to the square of the electric field instead of varying linearly with it.
Modelocking of a cw laser university of new mexico. For negative n2, the nonlinearity is selfdefocusing. Modelocking is a straightforward method to generate femtosecond pulses and kerr lens effect is a widespread way to lock the oscillator cavity modes. Slow saturable absorber and dynamic gain saturation. We report what is to our knowledge the first kerr lens mode locking of the visible transitions at 607 and 639 nm in pr31. Kerrlens mode locking without dispersion compensation. This method is analogous to kerr lens mode locking, although it is compatible with fiber lasers. The recipe to obtain kerr lens mode locking klm in the thindisk con guration is presented here and oscillator characteristics as well as startup diculties are described. The characteristics of kerrlens mode locked selframan nd. Such combined mechanism has the same effect as a saturable absorber. Kerrlens modelocked thindisk oscillator springerlink.
The procedure makes use of the fact that the gain of a frequency component of the radiation is. Active and passive mode locking cornell ece4300 fall 2016 duration. Analytical design of symmetrical kerrlens modelocking. This ratio may be enhanced in klm at the expense of cavity stability. The results indicate that the klm strength achieves its maximum value at. Control and manipulation of the kerr lens mode locking dynamics in lasers shai yefet department of physics ph. Kerr lens modelocking of solid state lasers with thermal. Directly diodepumped, kerrlens modelocked, fewcycle cr. Generation of 85 fs laser pulses from a diodepumped kerr. The corresponding spectral profile is shown in fig. Kerrlens mode locking resonator calculation with two. We have successfully constructed a softaperturing, asymmetric cavity kerr lens modelocked klm ti. T mode apm locking and kerr lens mode klm locking are developed. Opticalkerrenhanced mode locking of a lamppumped nd.
This effect is called selffocusing and has important implications for passive mode locking of lasers kerr lens mode locking and for optical damage of media catastrophic selffocusing. Experimental setup of the kerr lens mode locked klm alexandrite oscillator is schematically depicted in fig. The residential lens measures 7 516 length x 3 916 width x 2164 thick measured at outer edge and has 2 plastic tabs that protrude from the ends. Pdf energy scaling of kerrlens modelocked thindisk. A laser operated in this way is sometimes referred to as a femtosecond laser, for example in modern refractive surgery. Llf laser should provide some inspiration for the development of the blue ld pumped visible lasers, especially in the modelocking laser operation. Kerrlens modelocked highpower thindisk oscillators. Ultrafast lasers modelocked by nanotubes and graphene. Nevertheless, current mode locking technologies still suffer from drawbacks, e. Kerr lens mode locking is a powerful and wellknown method for generation of ultrashort pulses from solidstate lasers 10 and was adopted as mode locking mechanism in this work. Analytic theory of additive pulse and kerr lens mode locking. Optibond solo plus instructions for use kerr resources. Using the latter two techniques, pulses of less than 100 fs duration can be readily obtained.
Kerr lens mode locking without nonlinear astigmatism shai yefet, valery jouravsky, and avi peer department of physics and bina center of nanotechnology, barilan university, ramatgan 52900, israel. The basis of the technique is to induce a fixedphase relationship between the. This \ switch\ regulates transmission independently of external control depending on the eld amplitude of the radiation. Under the current approximations of the model, gainguiding decreases the value of the hardaperture mode locking parameter. Two dispersive mirrors introduce a group delay dispersion gdd of. The klm technique has been proposed many times and simultaneously criticized as difficult to realize 1, 2, 3.
They have been designed to support a broad spectral bandwidth and were. This document describes how 445nm laser diodes were successfully used to pump a soft. This method allows the generation of pulses of light with a duration as short as a few femtoseconds. An additive kerr medium is used for stable mode locked operation instead of semiconductor saturable absorber mirrors sesam, because kerr effect of the yb. The kerr effect induced selffocusing 1,2 during an intense pulse passing through a gain medium along focal range is exploited for modelocking 3.
Abstract we propose and theoretically investigate a novel operating regime of femtosecond kerr lens mode locked solidstate lasers that avoids groupvelocity dispersion compensation by use of a nonresonant semiconductor plate in the focused resonator section that provides an overall negative nonlinear refractive index per round trip. A meanfield model for kerr lens modelocking springerlink. In addition, sibbett and two research colleagues first demonstrated the kerr lens mode locking technique in a titaniumsapphire laser. Selffocusing in conjunction with an intracavity aperture creates a powerdependent amplitude modulation in laser oscillators, which allows passive mode locking.
Users can press the selflockinching mode button to switch between these two modes. We used for our calculations the sideband pump power of 6 w at 982 nm with 1 cm x 50 micrometers beam cross section in active medium and the length of 1 cm for kyw crystal. Active mode locking with picosecond pulse duration was realized in 2000, semiconductor saturableabsorber mirror sesam mode locking was demonstrated in 2005, and kerr lens mode locking was achieved in 2009. To overcome the disadvantages of nonlinear polarization rotation, we have been working on a new approach to mode locking fibers based on discrete spatial soliton formation in waveguide arrays. If the electronic kerr effect with response time of a few femtoseconds or less is used, a fast saturable absorber has been created. In this paper we want to present a new approach for the generation of subps parametric pulses starting with pump pulses of a few ps and introducing kerr lens mode locking 3 as a additional shortening mechanism besides temporal gain. It is known that kerr lens mode locking technique based on the nonlinear refractive index n2 of the laser medium itself is a manner for femtosecond laser pulse generation. The additional kerr lens in the pulsed laser mode equation 2 must be. Analytic theory of additive pulse and kerr lens mode.
The oscillator stability in terms of output power, beam. Construction of a wavelengthtunable selfstarting kerr lens mode. Multipulse operation and limits of the kerrlens modelocking stability vladimir l. Electrical engineering, technionisrael institute of tehcnologoy haifa 32000, israel 2research laborartoty of electronics, massachusetts institute of technology cambridge, ma 029 3 racah institute of physics, the hebrew university jerusalem 91904, israel. Assume slow saturable absorber and slow gain saturation net gain window. The latter effect causes a reduction in the beam size for high optical intensities. Yvo4 1176nm laser is demonstrated without any additional components, where the stimulated stokes raman scattering and kerr lens induced mode locking are operated in the same crystal. Rp photonics encyclopedia kerr lens mode locking, hard. Kerrs unique dental filling materials ensure professionals strike an ideal balance between ease of dispensing and optimal handling. Multipulse operation and limits of the kerr lens mode locking stability. For the love of physics walter lewin may 16, 2011 duration. Section 4 describes the fundamental concepts of kerr lens mode locking. On the contrary, kerr lens mode locking is known to support much shorter pulse durations 23, even beyond the emission.
Zns laser, generating 550 mw of 69 fs nearly transformlimited pulses at 2. A numerical model of kerrlens modelocking sciencedirect. Feb 01, 20 we report the softaperture kerrlens modelocked cr. A pulse that builds up in a laser cavity containing a gain medium and a kerr medium experiences not only selfphase modulation but also self focussing, that is nonlinear lensing of the laser beam, due to the nonlinear refractive in. Detailed design procedure for the kerr lens mode locked ti. The process of kerr lense mode locking klm introduced in the early 90s 23, allows to generate pulses of 10 femtoseconds fs duration and below in a rather simple way. A technique for mode locking a laser, exploiting nonlinear selffocusing. In a nutshell, kerr lens mode locking provides a means for producing femtosecond 1018 s laser pulses by conveniently exploiting a nonlinear optical effect in the laser crystal itself. Several types of cavity structures with which selfstarting operation of kerr lens mode locking lasers may be achieved are presented. Subsequently, these lasers were shown to generate ultrashort pulses through kerrlens modelocking. If for some reason you need to keep the aperture blades locked in a. Kerrlens mode locking klm is another technique that can be realized in a simple cavity without the need of an auxiliary cavity. We have developed a numerical model of kerrlens mode locking klm that includes astigmatism, nonlinear coupling and gainguiding.
Chapter 5 active mode locking forsimplicity, we assume, that the laser operates inthe transverse fundamental modes and, therefore, we only have to treat the longitudinal modes of the laser similar to a simple plane parallel fabryperot resonator figure. The ring cavity generates ultrashort pulse trains by means of softaperture kerr lens mode locking in either unidirectional or bidirectional lasing mode. Analytic theories of additive pulse mode apm locking and kerr lens mode klm locking are developed. Kerr lens mode locking resonator calculation with two nonlinear elements article in optics communications 18814. Analytical expressions for the spot size and the kerr lens mode locking lm strength can be represented as explicit functions of the position in the cavity, the laser power, and the stability parameter for a fourmirror figurez laser resonator. Representing the culmination of 20 years of inhouse expertise with kerr lens mode locking and thousands of cleanroom manufactured, industrialgrade ultrafast lasers, the vitara family satisfies the most sophisticated.
Yvo4 1176nm laser a selfstarting diodepumped picosecond nd. Kerr lens mode locking is a technique of passive mode locking a laser, using an artificial saturable absorber based on kerr lensing in the gain medium. Simulation of kerr lens modelocking behavior in sagittal. This method allows the generation of pulses of light with a. In singlecavity configurations, klm locking and apm locking produce comparable ratios of amplitude to phase modulation.
Sapphire laser with enhanced kerr nonlinearity, where the threshold for pulsed operation is lowered below the threshold for continuouswave operation. In this section, the mechanism of pulse formation is described in a qualitative and intuitive manner. Pdf cavitydumped femtosecond kerrlens mode locking in. Znse lasers 4, kerrlens mode locking klm in polycrystalline cr. Kerr lens mode locking klm is a method of mode locking lasers via the nonlinear optical kerr effect. A new technique called kerr lens mode locking klm has recently been developed which achieves fast saturable absorber action using selffocusing and. Yag lasers 2, but kerr lens mode locking is not performed for other ybdoped materials at this moment.
This has led to a number of mode locking techniques to obtain such pulses, for example acoustooptic, injection, synchronouspump, collidingpulse mode locking, and kerr lens mode locking. Sapphire lasers is that the mode locking can be achieved passively by exploring the optical kerr effect, which arises from a change in refraction index of an active medium when the intense laser pulses are generated. Frequency combs applications and optical frequency standards. Sesam allowed mode locking to selfstart, the resultant pulse duration of 180 fs was significantly longer than allowed by the gain medium. Femtosecond kerrlens modelocked thindisk oscillators constitute a peak and average power scalable oscillator concept.
Representing the culmination of 20 years of inhouse expertise with kerr lens modelocking and thousands of cleanroom manufactured, industrialgrade ultrafast lasers, the vitara family satisfies the most sophisticated. In the case of bidirectional mode locking, the repetition rates of the two outputs can be made identical or slightly different, depending on the cavity alignment. Cavitymode analysis of a kerrlens modelocked laser with a. Taking the cavity parameters that provide a most efficient mode locking and based on fluctuation model, we performed a numerical simulation of laser operation. A high spatial and spectral quality is achieved, close to the diffraction and fourier transform limitations.
Sf57 glass is used to stabilize the mode locked oscillation to decrease the intracavity loss to increase the oscillation bandwidth for transform limited pulse generation. Energy scaling of kerr lens mode locked thindisk oscillators article pdf available in optics letters 3922 november 2014 with 190 reads how we measure reads. This reduction in mode size inside the crystal acts as a soft aperture leading to kerr lens mode locking. It is developed with a view to modeling kerr lens mode locking, but promises much wider applicability. They provide a means for comparison of the two methods.
Modelocking is a technique in optics by which a laser can be made to produce pulses of light of extremely short duration, on the order of picoseconds 10. Selfstarting of passive mode locking ariel gordon1,2, omri gat1,3, baruch fischer1 and franz x. A pulse that builds up in a laser cavity containing a gain medium and a kerr medium experiences not only selfphase modulation but also self focussing, that is nonlinear lensing of the laser beam, due to the nonlinear refractive index of the kerr medium. Proceedings of spie the international society for optical engineering. The general principle behind kerrlens mode locking is sketched in fig. A bidirectional dualcomb ring laser for simple and robust. It could be realized in active photoniccrystal fibers with finite number of the air holes hexagonally arranged. Highpower kerrlens modelocked thindisk oscillator in. Examples are saturable absorbers or kerr lense modelocking. Kerr lens mode locking klm is a technique of passive mode locking a laser, using an artificial saturable absorber based on kerr lensing in the gain medium. To the best of our knowledge, this is the first demonstration of kerr. Modern dslr lenses dont usually have aperture rings, and opening and closing the aperture is the cameras responsibility.
For diodepumped all solid state lasers, klm operation is much more difficult mainly due to the low brightness and bad beam quality of the pump diode laser. If your base is white, you need the commercial 4 x 8 replacement lens. Since klm relies on the nonresonant kerr nonlinearity, it is independent of the lasing wavelength and bandwidth and gives ultrafast response. Multipulse operation and limits of the kerrlens modelocking.
Apr 24, 2001 the mechanism for selfstarting operation of kerr lens mode locking laser is studied. The average output power was 80 mw under a 4w diode pump power. The latter effect causes a reduction of the beam size for high intensities. For fourierlimited pulses the bandwidth is given by the inverse of the pulse duration, with a correction factor of order unity that depends on the pulse shape and. Joachim herrmann, theory of kerr lens mode locking. From the viewpoint of the beam divergence or m2 parameter for the abovementioned telescope the coma contribution to the beam divergence may be neglected at 2. The model also allows one to study the effect of elliptical astigmatic pump beams, typically encountered in.
Cavity mode analysis of a kerr lens mode locked laser with a novel fivemirror cavity. The optical kerr effect is a process which results from the nonlinear response of an optical medium to the electric field of an electromagnetic wave. Cavitydumped femtosecond kerr lens mode locking in a chromiumdoped forsterite laser. The laser used a slightly modified standard delta cavity. Optical kerr enhanced mode locking of a lamppumped nd. In addition, a general description is given to other mode locking techniques, which preceded kerr lens mode locking.
A mechanism of kerr lens mode locking in fiber laser is proposed and analyzed. Specifically, we provide a detailed description of the theoretical and experimental physics of a kerr lens mode locked klm ti. For passive modelocking we introduce a nonlinear\ switch\ to the resonator to suppress temporally long pulse components and support short pulses high intensities. Kerrlens modelocking klm is a method of modelocking lasers via the nonlinear optical kerr effect. The optical kerr effect is a process which results from the nonlinear response of an optical medium to the electric field of an. Pdf multipulse operation and limits of the kerrlens. When it comes to your dental composite filling needs, kerr is the brand you can trust. A simple analytical formalism yields closedform expressions for the depth of passive amplitude modulation introduced by either the spatial gain profile or a hard aperture inserted in the resonator. Kerr lens mode locking klm is a well developed technique for mode locking which has been widely used in femtosecond ti. With the help of a semiconductor saturable absorber mirror, stable mode locking with an average output power of 85mw at a repetition rate of 1mhz is realized.
1135 158 1268 903 146 1529 227 995 829 20 1019 1133 66 714 258 1166 385 1501 745 504 165 477 26 1232 432 1411 1410 357 1262 742 1112 1326 1213