| 1. |
- Grivas, Christos, et al.
(författare)
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Generation of Multi-Gigahertz Trains of Phase-Coherent Femtosecond Laser Pulses in Ti:Sapphire Waveguides
- 2018
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Ingår i: Laser & Photonics reviews. - : WILEY-V C H VERLAG GMBH. - 1863-8880 .- 1863-8899. ; 12:11
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Tidskriftsartikel (refereegranskat)abstract
- Miniature lasers producing ultrashort phase-coherent pulses at high repetition rates by stable mode-locking in ambient conditions can offer unique capabilities in various applications, spanning from microwave photonics to telecom and biological imaging techniques. Here, the operation of graphene mode-locked lasers based on channel waveguides written by femtosecond and picosecond laser pulses in Ti:sapphire crystals is demonstrated. Trains of pulses of 41.4 fs duration at a 21.25 GHz repetition rate are generated by capitalizing on the formation of solitons in their monolithic resonators through Gires-Tournois interferometers. The latter, allow for effective pulse shaping via tuning of the intracavity group delay dispersion while simultaneously enabling ultralow laser operating thresholds. A number of features of these sources, including their high-brightness and broad bandwidth, are essential ingredients for achieving high longitudinal resolution and sensitivity, which are the primary performance metrics of the Fourier domain/spectral domain variant of optical coherence tomography systems. A further doubling of the laser repetition rate to 42.5GHz is achieved by coherent pulse interleaving in optical fiber technology, thereby underlining the potential of the Ti:sapphire waveguide lasers to produce highly stable, wide-spaced combs of phase-coherent optical frequency lines.
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| 2. |
- Vazquez-Cordova, Sergio A., et al.
(författare)
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High gain in erbium-doped channel waveguides
- 2017
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Ingår i: 2017 CONFERENCE ON LASERS AND ELECTRO-OPTICS EUROPE & EUROPEAN QUANTUM ELECTRONICS CONFERENCE (CLEO/EUROPE-EQEC). - : IEEE.
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Konferensbidrag (refereegranskat)abstract
- Summary form only given. Integration of multiple functions on an optical micro-chip is going to revolutionize the exploitation of optics for various applications such as communication, optical sensing, and biomedicine. One of the enabling functions is amplification at 1.5 μm [1]. Rare-earth-doped amplifiers typically deliver a net gain per unit length of only a few dB/cm [2]. In spiral-shaped channel waveguides a total internal net gain of 20 dB was demonstrated [3].The rare-earth-doped potassium double tungstates KY(WO 4 ) 2 , KGd(WO 4 ) 2 , and KLu(WO 4 ) 2 are widely investigated laser materials [4]. They are especially suited for optical amplification due to the high transition cross-sections of rare-earth ions in these materials. Moreover, the large inter-ionic distance between neighboring rare-earth sites may allow for higher erbium concentrations without the detrimental effect of energy-transfer upconversion (ETU). Recently an internal net gain of ~1000 dB/cm was demonstrated in ytterbium-doped channel waveguides [2]. Here we report optical gain at 1.53 μm in KGd x Lu y Er 1-x-y (WO 4 ) 2 channel waveguides doped with five different Er 3+ concentrations. When pumping the Er 3+ ions at 980 nm, a record-high internal net gain of 13 dB/cm is experimentally demonstrated, despite the fact that the intrinsic propagation losses in these surface waveguides were as high as 4 dB/cm. Using buried channel waveguides, which typically exhibit intrinsic propagation losses of only 0.2 dB/cm, and optimizing the erbium concentration and waveguide length, for a reasonable 500 mW of launched pump power a high total gain of ~40 dB can be achieved.
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| 3. |
- Vazquez-Cordova, Sergio A., et al.
(författare)
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High optical gain in erbium-doped potassium double tungstate channel waveguide amplifiers
- 2018
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Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 26:5, s. 6260-6266
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Tidskriftsartikel (refereegranskat)abstract
- We report on the optical-gain properties of channel waveguides patterned into lattice-matched KGdxLuyEr1-x-y(WO4)(2) layers grown onto undoped KY(WO4)(2) substrates by liquid phase epitaxy. A systematic investigation of gain is performed for five different Er3+ concentrations in the range of 0.75 to 10at.% and different pump powers and signal wavelengths. In pump-probe-beam experiments, relative internal gain, i.e., signal enhancement minus absorption loss of light propagating in the channel waveguide, is experimentally demonstrated, with a maximum value of 12 +/- 5 dB/cm for signals at the peak-emission wavelength of 1534.7 nm.
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