Harmonic femtosecond fiber laser based on supercontinuum generation with carbon nanotubes saturable absorber

An ultrashort pulse fiber laser has been proposed due to the problem of bulky size and high cost of the Titanium Sapphire laser and other commercial ultrashort pulse fiber lasers. Thus, this study focused on the development of a robust, compact and stable femtosecond mode-locked fiber laser via optical telecommunication components. This laser was designed to have a high repetition rate (80 - 100 MHz) and average output power (30 - 50 mW), and also a narrow pulse width (< 100 fs) which are crucial for a laser source used in all-fiber terahertz time domain spectroscopy system. A short cavity was needed in order to get a high repetition rate while the effect of optical dispersion in the cavity was included in order to produce a narrow pulse width. This design employed a passive mode-locked technique with a carbon nanotube thin film as the saturable absorber. Initially, a diode laser of 980 nm wavelength was used as a pumping source and a 0.4 m long of highly erbium-doped fiber with 110 dB/m peak absorption at wavelength of 1530 nm was utilised as a gain medium. Then, in order to achieve the desired parameters, the pump power was increased to raise the repetition rate of the pulse laser and a supercontinuum generation technique was adopted to compress the pulse width. The preliminary results of the designed laser show a fundamental repetition rate of 67.8 MHz at mode-locking threshold pump power of 63.5 mW. The average output power and pulse width obtained are 0.77 mW and 410 fs respectively. The increment of pump power to 104.2 mW significantly increased the fundamental repetition rate to 193.5 MHz which corresponds to the 3rd order harmonic and compressed the pulse width to 70 fs. The average output power after compressing the pulse width is 4.27 mW. As the conclusion, two of the targeted parameters of the laser have been successfully attained. This design however has not been able to produce the targeted average output power and to operate with the desired parameters simultaneously

Optical Frequency Comb Generation based on Erbium Fiber Lasers

Citation: Droste, S., Ycas, G., Washburn, B. R., Coddington, I., & Newbury, N. R. (2016). Optical Frequency Comb Generation based on Erbium Fiber Lasers. Nanophotonics, 5(2), 196-213. doi:10.1515/nanoph-2016-0019Optical frequency combs have revolutionized optical frequency metrology and are being actively investigated in a number of applications outside of pure optical frequency metrology. For reasons of cost, robustness, performance, and flexibility, the erbium fiber laser frequency comb has emerged as the most commonly used frequency comb system and many different designs of erbium fiber frequency combs have been demonstrated. We review the different approaches taken in the design of erbium fiber frequency combs, including the major building blocks of the underlying mode-locked laser, amplifier, supercontinuum generation and actuators for stabilization of the frequency comb

Dispersion Measurement of Ultra-High Numerical Aperture Fibers covering Thulium, Holmium, and Erbium Emission Wavelengths

We present broadband group velocity dispersion (GVD) measurements of commercially available ultra-high numerical aperture fibers (UHNA1, UHNA3, UHNA4, UHNA7 and PM2000D from Coherent-Nufern). Although these fibers are attractive for dispersion management in ultrafast fiber laser systems in the 2 {\mu}m wavelength region, experimental dispersion data in literature is scarce and inconsistent. Here we demonstrate the measurements using the spectral interferometry technique covering the typically used erbium, thulium and holmium emission bands. The results are characterized in terms of the standard-deviation uncertainty and compared with previous literature reports. Fitting parameters are provided for each fiber allowing for the straightforward replication of the measured dispersion profiles. This work is intended to facilitate the design of ultrafast fiber laser sources and the investigations of nonlinear optical phenomena

Fiber Optic Devices Pumped with Semiconductor Disk Lasers

The aim of this thesis is to investigate the advantages of pumping fiber optic oscillators utilizing a special type of lasers – semiconductor disk lasers. Relatively novel semiconductor disk laser technology offers low relative intensity noise levels combined with scalable output power, stable operation and nearly diffraction-limited beam quality valuable for an efficient fiber coupling (70- 90%). This pumping technique was applied for optical pumping of fiber lasers. Low-noise fiber Raman amplifier in co-propagation configuration for pump and signal was developed in the 1.3 μm spectral range. A hybrid Raman-bismuth-doped fiber amplifier scheme for an efficient pump light conversion was proposed and demonstrated. Semiconductor disk lasers operating at 1.29 μm and 1.48 μm were used as the pump sources for picosecond Raman fiber lasers at 1.38 and 1.6 μm. The 1.38 μm passively modelocked Raman fiber laser produced 1.97 ps pulses with a ring cavity configuration. The 1.6 μm linear cavity fiber laser with the integrated SESAM produced 2.7 ps output. A picosecond semiconductor disk laser followed by the ytterbium-erbium fiber amplifier offered supercontinuum generation spanning from 1.35 μm to 2 μm with an average power of 3.5 W. By utilizing a 1.15 μm semiconductor disk laser, a pulsed Ho3+-doped fiber lasers for a 2 μm spectral band were demonstrated. 118 nJ pulses at the repetition rate of 170 kHz and central wavelength of 2097 nm were produced by a holmium fiber laser Q-switched by a carbon nanotube saturable absorber. Sub-picosecond holmium-doped fiber laser modelocked with a broadband carbon nanotube saturable absorber and a SESAM were developed. Using the former saturable absorber, ultrashort pulse operation with the duration of ~ 890 fs in the 2030-2100 nm wavelength range was obtained. The results in the presented dissertation demonstrate the potential of the semiconductor disk laser technology for pumping fiber amplifiers and ultrafast lasers

152 fs nanotube-mode-locked thulium-doped all-fiber laser.

Ultrafast fiber lasers with broad bandwidth and short pulse duration have a variety of applications, such as ultrafast time-resolved spectroscopy and supercontinuum generation. We report a simple and compact all-fiber thulium-doped femtosecond laser mode-locked by carbon nanotubes. The oscillator operates in slightly normal cavity dispersion at 0.055 ps(2), and delivers 152 fs pulses with 52.8 nm bandwidth and 0.19 nJ pulse energy. This is the shortest pulse duration and the widest spectral width demonstrated from Tm-doped all-fiber lasers based on 1 or 2 dimensional nanomaterials, underscoring their growing potential as versatile saturable absorber materials.We acknowledge funding from the Science and Technology Projects of Shenzhen City (JCYJ20150324140036862, JCYJ20140418095735546), the Natural Science Foundation of Guangdong Province (2015A030310464, 2016A030310049), the Scientific Research Foundation of Shenzhen City (827-000118), the Teknologiateollisuus TT-100, the European Union’s Seventh Framework Programme (REA grant agreement No. 631610), the Academy of Finland (No. 284548), Tekes (OPEC) and Aalto University (Finland). TH acknowledges funding from the Royal Academy of Engineering through a research fellowship (Graphlex).This is the final version of the article. It first appeared from Nature Publishing Group at http://dx.doi.org/10.1038/srep28885

New materials, regimes and applications of fibre laser technology

Nonlinear optics enables the manipulation of spectral and temporal characteristics of optical pulses interacting with a dielectric medium. Optical fibres, as a uniquely practical medium, provide an environment for effectively exploiting the nonlinear effects. This has facilitated the rapid growing interest in this field focused on the investigation of fibrebased sources incorporated with various novel saturable absorber devices for ultrashort pulse generation. This thesis reports a series of experiments exploring the ongoing research in the field of nonlinear optics, including the development of ultrafast mode-locked fibre sources and their applications in supercontinumm generation and third order parametric interactions in new carbon materials. Firstly, the integration of carbon-based materials with rare-earth doped media allows the demonstration of ultrafast mode-locked laser sources operating at wavelengths across the near-infrared region in a compact, low cost and environmentally robust scheme. Power scaling of such sources can be achieved by operating in the all-normal dispersion regime making use of a glass-substrate saturable absorber device that exhibits a higher damage threshold. Supercontinuum generation has been used as an effective method for spectral broadening. Pumping with a conceptually simple and reliable fibre-based system, a continuum covering from 2 to 3 μm is generated in a highly nonlinear GeO2 fibre. This experiment demonstrates a robust and long-term stable source of radiation in an important band, coincident with a portion of the atmospheric transmission window. Finally, the demonstration of a simple and compact nano-material based dual-wavelength system shows the performance of such devices as a simultaneous saturable absorber and passive synchroniser. An experimental study of coherent frequency mixing at large frequency shifts in a graphene sample, pumped by a two-colour fibre-integrated source, proves the strong nonlinear response of this new carbon material.Open Acces

Fiber-Based High-Power Supercontinuum and Frequency Comb Generation

Ultrafast optics has been a rich research field, and picosecond/femtosecond pulsed laser sources seek many applications in both the areas of fundamental research and industrial life. Much attention has been attached to fiber lasers in recent decades as they offering various superiorities over their solid-state counterparts with compact size, low cost, and great stability due to the inherent stability and safety of the waveguide structures as well as high photoelectric conversion efficiency. Fiber-based sources of ultrashort and high-peak/high-average optical pulses have become extremely important for high-precision laser processing while sources whose carrier-envelop offset and repetition rate are stabilized can serve as laser combs with applications covering many research areas, such as precision spectroscopy, optical clock, and optical frequency metrology. For the application as laser combs, four parts as fiber laser, broadband supercontinuum, nonlinear power amplification, and repetition rate stabilization must be concerned. This chapter is intended to give a brief introduction about the achievement of the four technologies mentioned above with different experimental setups, recently developed such as divided-pulse amplification (DPA) in emphasize. Moreover, detailed descriptions of the experimental constructions as well as theoretical analyses about the phenomena they produced are also involved