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. Pdf the abcdmatrix formalism is generalized for the description of self focusing and radially varying. Kerr lens mode locking is a technique for mode locking a laser, exploiting nonlinear selffocusing. By theoretical calculation of the group velocity dispersion in the laser gain, the compensation was employed for the realization of the continuouswave modelocked laser at the wavelength of 604 nm with the pulse width of 1. It is suitable for generating fewfemtosecond laser pulses. The collidingpulse mode locked cpm laser a lens and a lens kerr lens mode locking kerr lensing is. Multipulse operation and limits of the kerrlens mode. Kerrlens mode locking is caused by the self focusing.
For example, kerr lens mode locked lasers are often not selfstarting. 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 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. 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. 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. J pulses at an average power of 45 w opticaltooptical efficiency of 25%. Fernandez,1 nicola coluccelli,1,2 alessio gambetta,1,2 paolo laporta,1,2 and gianluca galzerano1,2, 1istituto di fotonica e nanotecnologie consiglio nazionale delle ricerche, piazza leonardo da vinci 32, 203 milano, italy 2dipartimento di fisica politecnico di milano, piazza. 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 2kmlabs inc. Pdf cavitydumped femtosecond kerrlens mode locking in. In addition, a general description is given to other mode locking techniques, which preceded kerr lens mode locking. Kerrlens mode locking is caused by the selffocusing. Zns laser, generating 550 mw of 69 fs nearly transformlimited pulses at 2. Kerrlens mode locking above a 20 ghz repetition rate. The average output power was 80 mw under a 4w diode pump power.
Measurements were taken in order to determine the mechanism behind the mode locking bias in these oscillators. At an increased 180 w pump power level, the laser produces 270 fs 1. Kerrlens mode locking resonator calculation with two. It generates pulses with a duration of 30 fs at a central wavelength of 1048 nm and a. This method allows the generation of pulses of light with a duration as short as a few femtoseconds. Directly diodepumped, kerrlens modelocked, fewcycle cr.
For negative n2, the nonlinearity is selfdefocusing. The ariati series feature compact size, userfriendly operation and longterm reliability. University of groningen ultrafast solvation dynamics explored. Threeelementcavity enables kerrlens modelocking at 20. Sapphire tis laser 12, common in almost every research laboratory engaged with ultrafast phenomena or high resolution spectroscopy. The other cavity arm had a pair of sf10 prisms p1 and p2 for dispersion compensation separated by 37 cm. Znse active medium predicts the strong defocusing cascaded secondorder nonlinearity within 2000 3000 nm spectral range. The theoretical calculation for nonlinear refractive index in cr. It is capable of producing up to a 60nm broadband spectrum and highpower mode locked output.
This equation can be derived by calculating the radially dependent nonlinear phase change. Sesam allowed mode locking to selfstart, the resultant pulse duration of 180 fs was significantly longer than allowed by the gain medium. 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. 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. Kerr lens mode locking has enabled the generation of the shortest pulses with durations down to. We demonstrate a powerscalable kerrlens modelocked yb. Multipulse operation and limits of the kerrlens modelocking stability vladimir l. Cagdalo 4 oscillator optically pumped by a bright fiber laser p. Kerrlens, modelocked lasers as transfer oscillators for.
Kerr lens mode locking resonator calculation with two nonlinear elements article in optics communications 18814. The article on passive mode locking explains how a saturable absorber leads to mode locking. Mode locking 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. 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. 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. Control and manipulation of the kerrlens modelocking. Using the latter two techniques, pulses of less than 100 fs duration can be readily obtained.
Our research is development of highaverage power kerr lens mode locked. All structured data from the file and property namespaces is available under the creative commons cc0 license. Currently, the generation of ultrashort optical pulses is dominated by the kerr lens mode locked ti. Files are available under licenses specified on their description page. Pulses as short as 85 fs at a central wavelength of 1074. Passive mode locking with an ideally fast saturable absorber semiconductor and dye lasers. Investigation of the kerrlens mode locking ability of cr. We report a direct bluediodepumped wavelength tunable kerr lens mode locked ti. Kerrlens mode locking klm is another technique that can be realized in a simple cavity without the need of an auxiliary cavity.
This arm of the cavity also contained a vertical slit to enable a hardaperture kerrlens modelocking. Central wave length tunability as broad as 89 nm 736825 nm is achieved by adjusting the insertion of the prism. Analytical design of symmetrical kerrlens modelocking laser cavities. Section 4 describes the fundamental concepts of kerr lens mode locking. The basis of the technique is to induce a fixedphase relationship between the. This has led to a number of modelocking techniques to obtain such pulses, for example acoustooptic, injection, synchronouspump, collidingpulse modelocking, and kerr lens modelocking. An undoped znse substrate was included in the resonator to provide enhanced nonlinear phase modulation during klm operation. A laser operated in this way is sometimes referred to as a femtosecond laser, for example in modern refractive surgery. Since klm relies on the nonresonant kerr nonlinearity, it is independent of the lasing wavelength and bandwidth and gives ultrafast response.
Znse laser with high spectral purity yuchen wang,1,2 toney t. Kerrlens mode locking above a 20 ghz repetition rate osa. Astigmatism in gaussianbeam selffocusing and in resonators for kerrlens mode locking. 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. Introduction one of the most popular sources of ultrashort pulse generation is the kerrlens modelocked klm titanium.
A 15ghz mode spacing optical frequency comb based on a kerr lens mode locked yb. Artificial saturable absorber mode locking apm and klm kerr lens mode locking klm chapter 7 pdf 1. Individual modes were clearly resolved by a commercial spectrometer. The general principle behind kerrlens mode locking is sketched in fig. I could only access this page via the modelocking page. Cavitydumped femtosecond kerr lens mode locking in a chromiumdoped forsterite laser. Pdf multipulse operation and limits of the kerrlens. Multipulse operation and limits of the kerrlens modelocking stability.
General features of this modelocking technique are discussed, and a procedure for the optimization of. Rp photonics encyclopedia kerr lens mode locking, hard. 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. Central wave length tunability as broad as 89 nm 736825 nm is. Its strength lies in the very fast response and the fact that no special saturable absorber medium is required. 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. It delivers 200 fs pulses at an average power of 17 w and a repetition rate of 40 mhz. 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. Persistent efforts by several research teams have produced rapid progress in mode locked cr. Kerrlens modelocking klm is a method of modelocking lasers via the nonlinear optical kerr.
Selffocusing in conjunction with an intracavity aperture creates a powerdependent amplitude modulation in laser oscillators, which allows passive mode locking. Kerr lens mode locking, kerr lens mode locking, kerr lens mode locking, kerr lens mode locking, kerr lens modelocking, kerr lens modelocking, kerr lens mode locking, kerr lens mode locking. What links here related changes upload file special pages permanent link page. Kerrlens modelocking klm is a method of modelocking lasers via the nonlinear optical kerr effect. The ariati series are broadband, kerrlens mode locked femtosecond oscillators with an integrated pump laser. Generation of 85 fs laser pulses from a diodepumped kerr. Lecture notes ultrafast optics electrical engineering. Pdf the abcdmatrix formalism is generalized for the description of selffocusing and radially varying.
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