Znse lasers 4, kerrlens mode locking klm in polycrystalline cr. Experimental setup of the kerr lens mode locked klm alexandrite oscillator is schematically depicted in fig. 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. Starting dynamic, selfstarting condition and modelocking threshold in passive, coupledcavity or kerrlens modelocked solidstate lasers. A high spatial and spectral quality is achieved, close to the diffraction and fourier transform limitations. Jan 02, 20 the kerr lens mode locking strength at the curved mirror was calculated over the stable range. In addition, a general description is given to other modelocking techniques, which preceded kerr lens modelocking. Active and passive mode locking cornell ece4300 fall 2016 duration. In the present case, mutual kerrlensing takes place in a zns crystal located at the center of the cavity, as shown in fig. The results indicate that the astigmatism is best compensated so. The results indicate that the astigmatism is best compensated so that the stable range of x and y. Pdf kerrlens mode locking without nonlinear astigmatism. Kerrlens modelocking klm is essentially a process of mimicking a fast saturable absorber inside a laser cavity by a combination of selfaction of the laser beam due to the optical kerr effect together with spatial aperturing 1517. Passive mode locking with an ideally fast saturable absorber semiconductor and dye lasers.
However, no matter what kind of modelocking mechanisms are applied, either kerrlens modelocking klm or passive modelocking with sesam or cnt, the shortest pulse generated from the yb. Analytical design of symmetrical kerrlens modelocking laser. We demonstrate a kerrlens mode locked folded cavity using a planar nonbrewster ti. 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. Measurements were taken in order to determine the mechanism behind the modelocking bias in these oscillators. Squier,1 matthew kirchner,2 greg taft,2 kevin shea,2 henry kapteyn,2,4 margaret murnane,2,4 and sterling backus2,3 1department of physics, colorado school of mines, golden, colorado 80401, usa. Kyw in the laser cavity, where not only the pump threshold to start modelocking but also the stable regions to maintain modelocking can be wellcontrolled. Our research is development of highaverage power kerrlens modelocked. We demonstrate a femtosecond kerr lens mode locked cr.
The optical kerr effect is a process which results from the nonlinear response of an optical medium to the electric field of an. 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. The design and alignment of these laser resonators have thus far been theoretically supported by the conventional analysis of beam propagation. In the case of kerrlens modelocking, a mechanism for creating multiple pulses is enhanced kerrlensing at the overlap of pulses in the ti. Pdf the abcdmatrix formalism is generalized for the description of selffocusing and radially varying pump power in a nonparabolic. Section 4 describes the fundamental concepts of kerr lens mode locking. The kerrlens modelocking strength at the curved mirror was calculated over the stable range. We demonstrate a kerr lens modelocked folded cavity using a planar nonbrewster ti. Since klm relies on the nonresonant kerr nonlinearity, it is independent of the lasing wavelength and bandwidth and gives ultrafast response. 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.
Our method uses a novel cavity folding in which the intracavity laser beam propagates in two perpendicular planes, such that. The general principle behind kerr lens mode locking is sketched in fig. 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 and aperture acts as a fast saturable absorber, then a fast passive gain modulation is obtained 5. We propose a new meanfield or master equation capable of describing transverse effects, pulse evolution and nonlinearity in an appropriate cavity. The intensity fluctuations in laser startup are not intense enough to induces kerr lensing 6,7, thus acoustooptic modulation, additive pulse modelocking, impulsive starting i. Passive modelocking using saturable absorbers an intracavity saturable absorber is able to fix phase of cavity modes variations slow saturable absorber fast saturable absorber kerrlens effect. Control and manipulation of the kerrlens modelocking. Lisgaf laser that based on a compact cavity geometry. Multipulse operation and limits of the kerrlens modelocking stability vladimir l. Generation of 85 fs laser pulses from a diodepumped kerr. Multipulse operation and limits of the kerrlens modelocking. Using the latter two techniques, pulses of less than 100 fs duration can be readily obtained.
Section 4 describes the fundamental concepts of kerr lens modelocking. Saturable gain and loss the passively modelocked dye laser some common dyes and their corresponding saturable absorbers colliding pulses have a higher peak intensity. Kerr lens mode locking klm is a method of mode locking lasers via the nonlinear optical kerr effect. Resolving the buildup of femtosecond modelocking with. The basis of the technique is to induce a fixedphase relationship between the longitudinal modes of the lasers resonant cavity. Kerrlens mode locking klm, simulating fast saturable absorber action, can achieve sub20fs pulses from ti. Experimental setup of the kerrlens modelocked klm alexandrite oscillator is schematically depicted in fig. 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. In the same framework, self starting of passive mode locking has the thermodynamic signi.
Ramanassisted broadband modelocked laser scientific reports. This method allows the generation of pulses of light with a duration as short as a few femtoseconds. A meanfield model for kerr lens modelocking springerlink. A new technique called kerr lens mode locking klm has recently been developed which achieves fast saturable absorber action using selffocusing and. Initially, mode locked tdls relied on semiconductor saturable absorber mirrors sesams. However, no matter what kind of mode locking mechanisms are applied, either kerr lens mode locking klm or passive mode locking with sesam or cnt, the shortest pulse generated from the yb. It has been recently understood that mode locking of lasers has the signi. The latter can be either due to the pumplaser mode overlap soft aperture or a physical hard aperture. Exploring ultrafast negative kerr effect for modelocking. Osa kerrlens mode locking above a 20 ghz repetition rate. One of the most successful schemes is called kerr lens mode locking klm, also sometimes called self mode locking.
Kerrlens modelocking klm is a well developed technique for modelocking which has been widely used in femtosecond ti. Kerr lens mode locking is a technique for mode locking a laser, exploiting nonlinear selffocusing. Kerr lens modelocking of a subpicosecond optical parametric. For the first time to our knowledge, with a combination of 488, 476 and 458nm lines from argonion laser as a pump source, 58fs pulses centered at 845 nm were generated.
Kerrlens modelocking klm is a method of modelocking lasers via the nonlinear optical kerr effect. Initially, modelocked tdls relied on semiconductor saturable absorber mirrors sesams. The availability of tdl crystals with broader gain emission bandwidths 14 allowed reducing the pulse duration of tdls from initially 680 fs 4 to 49 fs, which has been delivered at 2 w average output power 9. However, the wellestablished theoretical framework is sometimes beyond the scope of highpower oscillators, including recently developed thindisk. To date, passive mode locking methods such as kerr lens mode locking have been used to generate sub5fs pulses 1,2. 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. In the present case, mutual kerr lensing takes place in a zns crystal located at the center of the cavity, as shown in fig. Pdf kerr lens mode locking christian spielmann academia. 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. Pulses as short as 85 fs at a central wavelength of 1074. Kerrlens 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. In the case of kerr lens mode locking, a mechanism for creating multiple pulses is enhanced kerr lensing at the overlap of pulses in the ti. Analytic theory of additive pulse and kerr lens mode locking. The laser used a slightly modified standard delta cavity.
Our research is development of highaverage power kerr lens mode locked. It is developed with a view to modeling kerr lens modelocking, but promises much wider applicability. We demonstrate a femtosecond kerrlens modelocked cr. Rp photonics encyclopedia kerr lens mode locking, hard. Ultrashort pulses from kerrlens modelocked oscillators have inspired a variety of applications. By careful arrangement of an aperture in the laser cavity, this effect. Ultrashort pulse laser oscillators have been studied for the last halfcentury. One of the most successful schemes is called kerrlens modelocking klm, also sometimes called self modelocking. The general principle behind kerrlens mode locking is sketched in fig. To date, passive mode locking methods such as kerrlens mode locking have been used to generate sub5. The intensity fluctuations in laser startup are not intense enough to induces kerr lensing 6,7, thus acoustooptic modulation, additive pulse mode locking, impulsive starting i. 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. Selffocusing in conjunction with an intracavity aperture creates a powerdependent amplitude modulation in laser oscillators, which allows passive mode locking. Specifically, we provide a detailed description of the theoretical and experimental physics of a kerr lens mode locked klm ti.
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. Kerrlens modelocked highpower thindisk oscillators. The collidingpulse mode locked cpm laser a lens and a lens kerr lens mode locking kerr lensing is a type of saturable absorber. Kerr lens mode locking klm is another technique that can be realized in a simple cavity without the need of an auxiliary cavity. The collidingpulse modelocked cpm laser a lens and a lens kerrlens modelocking kerrlensing is a. Lyso laser is around 780 fs which is far beyond the limitation of. Mode locking can be achieved in a laser by the use of an active element. It is suitable for generating fewfemtosecond laser pulses. Geometrical analysis of kerrlens modelocking for highpeak. Kyw in the laser cavity, where not only the pump threshold to start mode locking but also the stable regions to maintain mode locking can be wellcontrolled. Thesis submitted to the senate of barilan university. We demonstrate a kerr lens mode locked folded cavity using a planar nonbrewster ti. In addition, a general description is given to other mode locking techniques, which preceded kerr lens mode locking. The latter effect causes a reduction in the beam size for high optical intensities.
The latter produces the shortest pulses and hence we shall be concerned with the dynamics of passive ml lasers. If you have a user account, you will need to reset your password the next time you login. Kerrlens mode locking klm is another technique that can be realized in a simple cavity without the need of an auxiliary cavity. In this section, the mechanism of pulse formation is described in a qualitative and intuitive manner. Kerrlens mode locking without nonlinear astigmatism. Paper open access simulation of femtosecond pulse in a kerr. Paper open access simulation of femtosecond pulse in a. Control and manipulation of the kerrlens modelocking dynamics in lasers shai yefet department of physics ph. Kerr lens mode locking without nonlinear astigmatism. General features of this modelocking technique are discussed, and a procedure for the. Get pdf abstract we present a compact, kerrlens modelocked oscillator consisting of a threeelement optical setup and demonstrate femtosecond pulse generation at a repetition rate of 23. This method allows the generation of pulses of light with a.
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