An additive kerr medium is used for stable mode locked operation instead of semiconductor saturable absorber mirrors sesam, because kerr effect of the yb. 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. Kgw oscillator with an additional kerr medium pumped by a highbrightness fibercoupled diode laser. Directly diodepumped, kerrlens mode locked, fewcycle cr. Znse active medium predicts the strong defocusing cascaded secondorder nonlinearity within 2000 3000 nm spectral range. Pdf energy scaling of kerrlens modelocked thindisk. 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. 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. 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.
Selfstarting of passive mode locking ariel gordon1,2, omri gat1,3, baruch fischer1 and franz x. Us6483858b1 injection modelocking tisapphire laser system. Cavitymode analysis of a kerrlens modelocked laser with. The generation of 72fs hyperbolic secant pulses centered at 1050nm with 17. For negative n 2, the nonlinearity is selfdefocusing. 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.
We have demonstrated a new method of mutual kerrlens modelocking which provides for a means to define the crossing point of counterpropagating waves in a ring or linear laser, without the use of a saturable absorber. All solidstate passively modelocked ultrafast lasers based. In addition the position of a hard or soft aperture similar as a fast saturable absorber in a klm laser is discussed. Saturable gain and loss the passively mode locked dye laser some common dyes and their corresponding saturable absorbers colliding pulses have a higher peak intensity. Yag lasers 2, but kerr lens mode locking is not performed for other ybdoped materials at this moment. All structured data from the file and property namespaces is available under the creative commons cc0 license. Although still commonly used, conventional active and passive mode locking have been supplanted by a new technique, kerr lens mode locking, for the generation of very short pulses. Kerr lens mode locking has enabled the generation of the shortest pulses with durations down to. Several types of cavity structures with which selfstarting operation of kerr lens mode locking lasers may be achieved are presented. We propose a new meanfield or master equation capable of describing transverse effects, pulse evolution and nonlinearity in an appropriate cavity. Octavespanning lasers for optical metrology applications. A laser cavity includes a gain medium for amplifying a light pulse in a light path, wherein the gain medium has a gain profile for amplifying the light pulse as a function of wavelength. Al 2o 3 laser achieved by use of an extended cavity design is demonstrated.
This document provides supplementary information to directly diodepumped. The collidingpulse mode locked cpm laser a lens and a lens kerr lens mode locking kerr lensing is a type of saturable absorber. Files are available under licenses specified on their description page. Ultrashort laser pulses are considered to be those whose pulse duration is less than a few picoseconds 1012 s long. First demonstration of harmonic modelocking in a selfmode. This method is analogous to kerr lens mode locking. Research in germany has produced the first demonstration of harmonic modelocking in a self. The actual size for a pdf page is typically 100%, but the document may have been set to another magnification level when it was created. This method allows the generation of pulses of light with a duration as short as a few femtoseconds.
The high power fundamental laser at 42 nm was generated efficiently with a sidepump nd. In this section, the mechanism of pulse formation is described in a qualitative and intuitive manner. In particularly, based on the passive mode locking mechanism, the kerr lens mode locking klm ti. Moreover, klm does not require a sophisticated design and manufacturing process. Pdf multipulse operation and limits of the kerrlens. Astigmatism in gaussianbeam selffocusing and in resonators for kerrlens mode locking. Ramanassisted broadband modelocked laser scientific reports. Us8798106b2 modelocking with reduced nonlinearity using. The collidingpulse mode locked cpm laser a lens and a lens kerr lens mode locking kerr lensing is. 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. 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. Kerr lens and additive pulse mode locking soft aperture hard aperture gain.
The mechanism for selfstarting operation of kerr lens mode locking laser is studied. Femtosecond kerrlens modelocked thindisk oscillators constitute a peak and average power scalable oscillator concept. Modelocking of a cw laser university of new mexico. 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.
On the contrary, kerr lens mode locking is known to support much shorter pulse durations 23, even beyond the emission bandwidthlimit of the laser gain medium 43,44. It is developed with a view to modeling kerr lens mode locking, but promises much wider applicability. Caf 2 reported significant improvements in average power of bulk oscillators with the generation of sub 70 fs with several watts 8. Femtosecond laser pulses in a kerr lens modelocked thin. Ylf laser, initiated by means of a liquid saturable absorber. It is suitable for generating fewfemtosecond laser pulses. We configured kerrlens modelocked lasers based on yb. Passive mode locking using saturable absorbers an intracavity saturable absorber is able to fix phase of cavity modes variations slow saturable absorber fast saturable absorber kerr lens effect. Analysis of laser cavities with selfstarting kerrlens mode.
Cavity mode analysis of a kerr lens mode locked laser with a novel fivemirror cavity. Blue radiation emanating from the crystal has been identified as surface second harmonic and sum frequency generation. A technique for mode locking a laser, exploiting nonlinear selffocusing. Abstract this document describes how 445nm laser diodes were successfully used to pump a soft aperture kerr lens modelocked ti. Multipulse operation and limits of the kerrlens modelocking stability vladimir l. Cavity mode analysis of a kerrlens mode locked laser with a novel fivemirror cavity. We experimentally demonstrate that this method opens up the route to phaselink signals with arbitrary frequencies in the optical or microwave range while their frequency stability is. On the basis of this result the optimal cavity configuration for kerr lens mode locking is proposed that allows to achieve a sub100 fs pulse duration. A meanfield model for kerr lens modelocking springerlink. Analysis of laser cavities with selfstarting kerrlens. We introduce a novel concept for optical frequency measurement and division which employs a kerr lens, mode locked laser as a transfer oscillator whose noise properties do not enter the measurement process.
Kerr lens mode locking klm is a method of mode locking lasers via the nonlinear optical kerr effect. Kerrlens mode locking is caused by the self focusing. Cavitymode analysis of a kerrlens modelocked laser with a. Recent research has led to techniques such as kerr lens mode locking to enable pulse duration. Thesis submitted to the senate of barilan university. Kerr lens mode locking klm technique combined with highbrightness pumping. Pulses as short as 85 fs at a central wavelength of 1074. Multipulse operation and limits of the kerrlens modelocking. Intensity autocorrelation of a representative pulse width recorded at 607 nm from the kerr lens mode locked pr. Multipulse operation and limits of the kerr lens mode locking stability. Its strength lies in the very fast response and the fact that no special saturable absorber medium is required. Abstract this document describes how 445nm laser diodes were successfully used to pump a soft aperture kerr lens mode locked ti.
This is an important step, since kerr lens mode locked ti. Such combined mechanism has the same effect as a saturable absorber. 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. Download pdf 584 kb abstract the kerrlens mode locking stability and the ultrashort pulse characteristics are analyzed numerically for the crdoped znte, znse, zns active media. The theoretical calculation for nonlinear refractive index in cr.
In addition, sibbett and two research colleagues first demonstrated the kerr lens mode locking technique in a titaniumsapphire laser. Proceedings of spie the international society for optical engineering. Vier optics communications 115 1995 533538 i april 1995 optics communications kerr lens mode locking of a subpicosecond optical parametric oscillator r. Ultrafast lasers modelocked by nanotubes and graphene. The average output power was 80 mw under a 4w diode pump power. Kerr lens mode locking without nonlinear astigmatism.
To demonstrate graphene mode locking of the alexandrite laser, we adopt a resonator configuration similar to what was previously used for kerr lens mode locking experiments 20. Generation of 85 fs laser pulses from a diodepumped kerr. Kerr lens modelocking how is kerr lens modelocking abbreviated. We have demonstrated a highpower kerr lens mode locked yb. If you have a disability and are having trouble accessing information on this website or need materials in an alternate format, contact web. These advances, in particular the realization of new modelocking technologies, have. Multipulse operation and limits of the kerrlens mode. Kerrlens modelocking 14 and semiconductor saturable absorber mirrors sesams 46 have changed the outlook of ultrafast lasers over the past two decades. Kerr lens mode locking is a technique for mode locking a laser, exploiting nonlinear selffocusing. 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. Directly diodepumped, kerrlens modelocked, fewcycle cr.
The most common example of this is kerr lens modelocking of titaniumsaphhire ti. 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. Analytic theory of additive pulse and kerr lens mode. 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. Apr 24, 2001 the mechanism for selfstarting operation of kerr lens mode locking laser is studied. Using the latter two techniques, pulses of less than 100 fs duration can be readily obtained. In addition, mode locked lasers represent a unique system in which to study the propagation of optical pulses. October 2019 learn how and when to remove this template message. The general principle behind kerrlens mode locking is sketched in fig.
By theoretical calculation of the group velocity dispersion in the laser gain, the compensation was employed for the realization of the continuouswave mode locked laser at the wavelength of 604 nm with the pulse width of 1. On the contrary, kerr lens mode locking is known to support much shorter pulse durations 42, even beyond the emission bandwidthlimit of the laser gain medium 43, 44. Selffocusing in conjunction with an intracavity aperture creates a powerdependent amplitude modulation in laser oscillators, which allows passive mode locking. Section 4 describes the fundamental concepts of kerr lens mode locking. Kerr lens modelocking of a subpicosend optical parametric. Compared with the active mode locking technique, passively mode locked laser with saturable absorber is able to generate much shorter pulse with a simple configuration. In addition, a general description is given to other mode locking techniques, which preceded kerr lens mode locking. The general principle behind kerr lens mode locking is sketched in fig. The optical kerr effect is a process which results from the nonlinear response of an optical medium to the electric field of an.
In general, modelocking establishes preference for pulsed operation, either in loss or. Kerrlens, modelocked lasers as transfer oscillators for. Pdf the abcdmatrix formalism is generalized for the description of selffocusing and radially varying. Design issues for this modelocking technique are discussed. 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. Highpower simultaneously qswitched and kerrlens mode. Control and manipulation of the kerrlens modelocking dynamics in lasers shai yefet department of physics ph. However, kerr lens mode locking is not selfstarting 1,11.
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. Ultrashort optical pulses are produced by mode locked lasers. Feb 01, 20 we report the softaperture kerrlens modelocked cr. Kerrlens mode locking is caused by the selffocusing. A multiwatt, multighz laser eyesafe laser was obtained by simultaneously qswitched kerr lens mode locking and stimulated raman scattering. Rp photonics encyclopedia kerr lens mode locking, hard. We have demonstrated a new method of mutual kerr lens mode locking which provides for a means to define the crossing point of counterpropagating waves in a ring or linear laser, without the use of a saturable absorber. Our group is doing research on new ways to mode lock lasers, specifically fiber lasers.
Mode locking thresholds as low as 156 mw are achieved. In singlecavity configurations, klm locking and apm locking produce comparable ratios of amplitude to phase modulation. Therefore, boosting up the peak power of femtosecond pulses in a kerr lens mode locked thindisk oscillator can accelerate the progress of application of thindisk oscillators in the scienti. Thindisk technology uniquely enables the simultaneous scaling of both average and peak powers, while maintaining an excellent beam profile. Kerrlens modelocked highpower thindisk oscillators. Investigation of the kerrlens mode locking ability of cr. Yag is an attractive material for highpower and ultrashort pulse laser because of its high quantum efficiency exceeding 90% and wide gain spectrum larger than about 10 nm. Kerrlens modelocking klm is a method of mode locking lasers via the nonlinear optical kerr effect. Passive mode locking can typically achieve pulses as short as a few picoseconds in broad bandwidth solidstate materials. Pdf the abcdmatrix formalism is generalized for the description of self focusing and radially varying. Laubereau physik department ell, technische universitdt munchen, 85748 garching.
According to the present invention there is provided an injection modelocking tisapphire laser system that produces a unidirectional laser oscillation through the application of a ring cavity laser that incorporates no intracavity devices to achieve unidirectional oscillation. Passive mode locking with an ideally fast saturable absorber semiconductor and dye lasers. Realization of a kerrlens modelocked verticalexternalcavity. Analytical design of symmetrical kerrlens modelocking laser cavities. Control and manipulation of the kerrlens modelocking. The shortest pulses are produced by passive mode locking, typically based on an effective saturable absorber that utilizes the nearinstantaneous kerr effect. Learn how and when to remove this template message. Energy scaling of kerrlens modelocked thindisk oscillators article pdf available in optics letters 3922 november 2014 with 190 reads how we measure reads. The article on passive mode locking explains how a saturable absorber leads to mode locking. On the contrary, kerr lens mode locking is known to support much shorter pulse durations 23, even beyond the emission. Ultrashort laser pulses carlo antoncini department of physics university of reading whiteknights, reading, rg6 6af, uk abstract.
Sesam allowed mode locking to selfstart, the resultant pulse duration of 180 fs was significantly longer than allowed by the gain medium. Kerrlens modelocking klm is a method of modelocking lasers via the nonlinear optical kerr. Analytic theories of additive pulse mode apm locking and kerr lens mode klm locking are developed. Joachim herrmann, theory of kerr lens mode locking. The fundamental laser was captured by the intracavity raman cavity, and the mode beating of the fundamental laser and the. Vier optics communications 115 1995 533538 i april 1995 optics communications kerr lens modelocking of a subpicosecond optical parametric oscillator r. If the electronic kerr effect with response time of a few femtoseconds or less is used, a fast saturable absorber has been created.