98 research outputs found

    High repetition rate fiber lasers

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 117-121).This thesis reports work in high repetition rate femtosecond fiber lasers. Driven by the applications including optical arbitrary waveform generation, high speed optical sampling, frequency metrology, and timing and frequency distribution via fiber links, low noise fiber laser sources operating at multi-gigahertz repetition rates are developed systematically. A 200 MHz fundamentally mode-locked soliton laser and a 200 MHz fundamentally mode-locked similariton laser are first developed. Intra-cavity soliton formation is recognized as the optimum route towards achieving high fundamental repetition rates compact lasers, under the limitation of realistically available pump power. A 3 GHz fundamentally mode-locked femtosecond fiber laser is developed and verifies the soliton formation theory. Techniques in external cavity repetition rate multiplications are also discussed. A theoretical model that relates the repetition rate of the soliton laser and its other physical measurable parameters is developed to guide further high repetition rate laser development.by Jian Chen.Ph.D

    Sub-100 fs watt-level Kerr-lens mode-locked Yb:CaYAlO4 laser with a gigahertz repetition rate

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    We report a 1.04 GHz high-power Kerr-lens mode-locked Yb:CaYAlO4 laser pumped by a single-mode fiber laser at 976 nm. Based on a bow-tie cavity, stable unidirectional mode-locked operation is obtained with an output coupler of 1.6%. The oscillator delivers pulses with an average power of 1.46 W and with the pulse duration of 99 fs, which, to the best of our knowledge, is the first gigahertz-level Kerr-lens mode-locked laser based on the Yb:CaYAlO4 gain medium. We believe that the watt-level solid-state femtosecond laser at GHz would be an excellent source for developing time-resolved broadband dual-comb spectroscopy

    Carrier-Envelope Offset Stabilized Ultrafast Diode-Pumped Solid-State Lasers

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    Optical frequency combs have been revolutionizing many research areas and are finding a growing number of real-world applications. While initially dominated by Ti:Sapphire and fiber lasers, optical frequency combs from modelocked diode-pumped solid-state lasers (DPSSLs) have become an attractive alternative with state-of-the-art performance. In this article, we review the main achievements in ultrafast DPSSLs for frequency combs. We present the current status of carrier-envelope offset (CEO) frequency-stabilized DPSSLs based on various approaches and operating in different wavelength regimes. Feedback to the pump current provides a reliable scheme for frequency comb CEO stabilization, but also other methods with faster feedback not limited by the lifetime of the gain material have been applied. Pumping DPSSLs with high power multi-transverse-mode diodes enabled a new class of high power oscillators and gigahertz repetition rate lasers, which were initially not believed to be suitable for CEO stabilization due to the pump noise. However, this challenge has been overcome, and recently both high power and gigahertz DPSSL combs have been demonstrated. Thin disk lasers have demonstrated the highest pulse energy and average power emitted from any ultrafast oscillator and present a high potential for the future generation of stabilized frequency combs with hundreds of watts average output power

    Versatile silicon-waveguide supercontinuum for coherent mid-infrared spectroscopy

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    Infrared spectroscopy is a powerful tool for basic and applied science. The molecular spectral fingerprints in the 3 um to 20 um region provide a means to uniquely identify molecular structure for fundamental spectroscopy, atmospheric chemistry, trace and hazardous gas detection, and biological microscopy. Driven by such applications, the development of low-noise, coherent laser sources with broad, tunable coverage is a topic of great interest. Laser frequency combs possess a unique combination of precisely defined spectral lines and broad bandwidth that can enable the above-mentioned applications. Here, we leverage robust fabrication and geometrical dispersion engineering of silicon nanophotonic waveguides for coherent frequency comb generation spanning 70 THz in the mid-infrared (2.5 um to 6.2 um). Precise waveguide fabrication provides significant spectral broadening and engineered spectra targeted at specific mid-infrared bands. We use this coherent light source for dual-comb spectroscopy at 5 um.Comment: 26 pages, 5 figure

    High-repetition-rate Yb-doped lasers for frequency comb generation

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    The research presented in this thesis addresses the development of directly diode pumped Yb3+:KY(WO4)2 and Yb: bre lasers, operating at several-hundred-MHz repetition frequencies and investigates their suitability as the basis of high-e ciency, convenient, low-cost and moderate precision optical frequency combs. The design, construction, and characterisation of a 1042-nm 1-GHz Yb3+:KY(WO4)2 femtosecond laser is presented, achieving pulses with an average power output of 770 mW, bandwidths of 3.8 nm, and durations of 278 fs. The laser achieved an opticalto- optical conversion e ciency and slope e ciency of 61% and 69%, respectively, and the relative intensity noise was <0.1%. Spectral broadening of the output pulses in a photonic crystal bre with a negative dispersion wavelength of 975 nm and a core diameter of 3.7 m resulted in a supercontinuum with a bandwidth of 400 nm, which was insu cient to enable f-2f referencing. A re-designed Yb:KYW laser was demonstrated, operating at a pulse repetition frequency of 666 MHz and producing pulses with reduced durations of 220 fs and increased bandwidths of 5 nm, while maintaining an average output power of >700 mW. Repetition-frequency locking was implemented on this laser and had the e ect of reducing its relative intensity noise from 1.1% to 0.5%, with limitations on the locking stability being traced to cantilever-like vibrational modes of the mirrormount assemblies. A fully stabilised 1030-nm Yb: bre frequency comb operating at a pulse repetition frequency of 375 MHz was developed. The comb spacing was referenced to a Rb-stabilised microwave synthesiser and the comb o set was stabilised by generating a supercontinuum containing a coherent component at 780.2 nm, which was heterodyned with a 87Rb-stabilised external cavity diode laser to produce a radiofrequency beat used to actuate the carrier-envelope o set frequency of the Yb: bre laser. The two-sample frequency deviation of the locked comb was 235 kHz for an averaging time of 50 seconds, and the comb remained locked for over 60 minutes with a root mean squared deviation of 236 kHz

    Novel optical fibre based laser sources for spectral and temporal versatility

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    As laser amplifiers and oscillators continue to see widespread use in all branches of science and engineering, they continue to develop in terms of operating parameters to keep pace with their applications. Importantly, the temporal and spectral characteristics of laser systems must be carefully tailored to match application requirements. This thesis reports advances in the development of laser systems, based upon optical fibre technology, which demonstrate the flexibility of optical fibre and fibre integrated devices to cover a wide range of temporal and spectral characteristics. First, the principle of spectrally masked phase modulation for short pulse generation is explored. Here, a phase modulator is used to generate a time dependent optical frequency shift, which can be turned into an effective amplitude modulation by the introduction of an optical band pass filter. This method is combined with nonlinear compression techniques based on solitonic propagation in optical fibre to generate optical pulses with duration of a few hundreds of femtoseconds and repetition rates of tens of gigahertz. Increasing the range of wavelengths over with doped fibre amplifier systems will operate requires the development of laser/amplifier systems based on new active dopants. To this end amplifier systems based upon bismuth activated alumosilicate fibre were evaluated. The amplifier stages were then incorporated into a master oscillator power fibre amplifier (MOPFA) scheme, demonstrating the applicability of bismuth doped silica fibre to advanced laser configurations. Finally, the development of a novel laser source for use in fluorescent microscopy is detailed. The source was based on a gain switched diode which is amplified in a two stage Raman fibre amplifier system, subsequently frequency doubled in a periodically poled lithium tantalate crystal. Nonlinearity and optical filtering are exploited to re-shape the output pulse's temporal profile.Open Acces
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