Passively mode locked femtosecond Tm:Sc_2O_3 laser at 21 μm

Abstract

We report on the passive mode locking of a Tm 3 :Sc 2 O 3 laser at 2.1 μm using a semiconductor saturable absorber mirror based on InGaAsSb quantum wells. Transform-limited 218 fs pulses are generated with an average power of 210 mW. A maximum output power of 325 mW is produced during mode locking with the corresponding pulse duration of 246 fs at a pulse repetition frequency of 124.3 MHz. A Ti:sapphire laser is used as the pump source operating at 796 nm. © 2012 Optical Society of America OCIS codes: 140.4050, 140.7090, 140.5680, 140.3070, 140.3580, 160.3380. Ultrashort-pulse lasers that operate in the 2 μm spectral region and produce relatively high average powers (100s of milliwatts and above) are of particular interest for the development of broadband coherent sources such as optical parametric oscillators or supercontinua in the mid-IR (∼2-10 μm) spectral region. , and the three-dimensional microstructuring of semiconductors [7]. So far, only a few lasers capable of producing nanojoule-energy femtosecond pulses around 2 μm have been demonstrated [8,9]. These include a Tm-doped fiber laser that was passively mode locked using an additive-pulse mode-locking technique to produce pulses with energies of up to 4 nJ (167 mW of average power) that were compressed externally to a duration of 173 fs. However, this involved a rather complex configuration that required a combination of fiber and free-space optics as well as an external-cavity pulse compressor.Recently, we have demonstrated the efficient generation of femtosecond pulses directly from Tm-doped and Tm,Ho codoped solid-state crystalline lasers by using a semiconductor saturable absorber mirror (SESAM) for passive mode locking [10][11][12]. In particular, 191 fs pulses were produced from Tm, Ho:NaYWO 4 2 around 2060 nm and a Tm:KYWO 4 2 laser generated 386 fs pulses with an average power of 235 mW at 2029 nm. Regarding further development of diode-pumped, high-power, 2 μm solidstate femtosecond lasers, Tm-doped crystals having characteristic broadband and relatively homogeneous gain spectra (preferably extending beyond 2 μm) and accompanying good thermomechanical properties represent excellent candidate gain media. In this respect, the recently investigated Tm-doped sesquioxide crystals (Lu 2 O 3 and Sc 2 O 3 ) that possess high thermal conductivities and demonstrate efficient and high-power cw operation in the range ∼1930-2150 nm are especially interesting [13,14]. It should be noted that long wavelength generation (>2 μm) from a Tm-laser is advantageous for stable passive mode locking because the presence of strong water vapor absorption bands in the ∼1800-2000 nm region can prevent broadband mode locking and give rise to Q-switching instabilities. Previously, only passive mode locking of a Tm:Lu 2 O 3 laser has been reported. This system incorporated a carbon nanotube saturable absorber to produce 31 ps pulses at 1965 nm [15].Here we report, for the first time to our knowledge, the passive mode locking of a Tm-doped Sc 2 O 3 laser by utilizing a qua...

Rare-Earth-Doped Sesquioxides for Diode-Pumped High-Power Lasers in the 1-, 2-, and 3-μm Spectral Range

“…Utilizing Tm 3+ (1%):Sc 2 O 3 as the gain material, SESAM mode-locked pulses as short as 218 fs with a spectral bandwidth of more than 20 nm have been realized at 210 mW of average output power and 120 MHz repetition rate under Ti:sapphire pumping [79]. In these experiments a filter ensured laser operation beyond 2050 nm to match the emission of the laser to the saturable absorption characteristics of the absorber.…”

Offset-Free Gigahertz Midinfrared Frequency Comb Based on Optical Parametric Amplification in a Periodically Poled Lithium Niobate Waveguide

“…Various approaches have recently been pursued to extend the spectral coverage of frequency combs into the mid-infrared [10]. Direct approaches include new laser gain materials for modelocked solid-state and fiber lasers [11][12][13] or semicon-ductor devices such as quantum cascade lasers [14,15]. Another approach relies on exploiting different aspects of nonlinear optics, such as supercontinuum generation (SCG) in fibers [16][17][18] and waveguides [19][20][21], or Kerr comb generation in microresonators [22,23].…”

2-$\mu\hbox{m}$ Tm-Doped All-Fiber Pulse Laser With Active Mode-Locking and Relaxation Oscillation Modulating

“…Mode-locking and Q-switching are two common methods to generate pulse laser [1]- [8]. Most of the reported mode-locked Tm-doped pulse lasers are realized by passive mode-locking, using semiconductor saturable absorber mirror (SESAM) [1]- [4] or graphene saturable absorber (GSA) [5], [6]. As for active mode-locking, Eckerle et al reported an actively mode-locked Tm-doped fiber laser based on bulk optics component using acousto-optic modulator (AOM) [8].…”