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Item Open Access 1.06μm-1.35μm coherent pulse generation by a synchronously-pumped phosphosilicate Raman fiber laser(OSA, 2017) Elahi, Parviz; Makey, Ghaith; Turnalı, Ahmet; Tokel, Onur; İlday, Fatih ÖmerSummary form only given. Rare-earth-doped fiber lasers are attractive for microscopy and imaging applications and have developed over the past decades rapidly. They are unable to cover near-infra-red region entirely and therefore Raman and parametric process are promising for producing new wavelengths which are out of emission band of the current fiber lasers. Here, we demonstrate a synchronously-pumped Raman laser system for producing coherent signals spanning from 1.06 μm to 1.35 μm. The laser system comprises a passively-mode-locked oscillator, two stages of amplifier and a phosphosilicate Raman oscillator. The schematic of experimental setup is shown in Fig. 1(a). A mode locked oscillator operating at 37 MHz is using as a seed source. The output pulse duration and central wavelength are 6 ps and 1065 nm, respectively. 6 mW output from oscillator is launched to pre amplifier comprises 85-cm long Yb 401-PM pumped by a single mode diode through a PM wavelength division multiplexer (WDM). The power amplifier consists of a 3.5-m long Yb 1200-DC-PM with 6 μm core diameter and 125 μm cladding diameter pumped by a temperature stabilized, high power multimode diode laser via a multimode pump-signal combiner (MPC). A 30/70 coupler is employed for delivering pump signal at 1060 nm to the Raman oscillator comprises 4.2-m long ph-doped fiber. To synchronize pump and Raman and achieve coherent pulses, we adjust the length of cavity by a precise translation stage. By using proper filter inside the Raman cavity, different wavelengths are achieved.Item Open Access 1.7-GHz intra-burst repetition rate Yb-fiber amplifier system(IEEE, 2015) Kalaycıoğlu, Hamit; Elahi, Parviz; Kerse, Can; Akçaalan, Önder; İlday, F. ÖmerMaterial processing efficiency of ultrafast pulses increases dramatically with repetition rate of the pulses, if the conditions are adjusted correctly to avoid excessive plasma and particulate shielding. However, given that there is a minimum pulse energy requirement, continuous operation at high repetition rates can be detrimental due to too much average power leading to heat accumulation. Burst-mode operation of lasers, wherein the amplifier periodically produces a group of pulses (a burst), which are very closely spaced in time, avoids this problem. However, ultrafast burst-mode lasers are typically limited to several 100 MHz intra-burst repetition rates. While this is sufficient for most materials, metals with high thermal conductivity require higher repetition rates.Item Open Access 10 W, 10 ns, 50 kHz all-fiber laser at 1.55 µm(Optical Society of America, 2012) Pavlov, Ihor; Dülgergil, E.; İlbey, Emrah; İlday, Fatih ÖmerWe report on an all-fiber, singlemode MOPA system at 1.55 µm producing 10-ns, 200-µJ pulses with 20 kW of peak power and utilize it to micromachine crystalline Si, which is largely transparent at this wavelength.Item Open Access 10 μJ 150 fs all-fiber Yb laser amplifier system(IEEE, 2015) Akçaalan, Önder; Kalaycıoğlu, Hamit; Kesim, Denizhan Koray; İlday, F. ÖmerFemtosecond laser pulse sources have become increasingly popular in the last decade as a result of their practical features, such as insensitivity to environmental variations, versatile designs, high-power outputs. However, much of the progress is with non-integrated specialty fibers, which involve some compromise on these practical features. Monolithic fiber chirped pulse amplification (CPA) systems are very attractive for industrial and scientific applications due to the features such as compactness, reliability and robustness [1].Item Open Access 10-W, 156-MHz all-fiber-integrated Er-Yb-doped fiber laser-amplifier system(Optical Society of America, 2012) Pavlov, Ihor; İlbey, Emrah; Dülgergil, Ebru; İlday, Fatih ÖmerWe demonstrate all-fiber, high-power chirped-pulse-amplifier system, operating at 1550 nm. 156-MHz soliton oscillator seeds a two-stage single-mode amplifier with output power of 10 W. After external compression, pulse duration is 0.6 ps. © 2012 Optical Society of America.Item Open Access 20-fs 1.6-mJ pulses from a cw-diode-pumped single-stage 1-kHz Yb amplifier(OSA, 2010) Andriukaitis, G.; Kartashov, D.; Pugzlys, A.; Lorenc, D.; Baltuska, A.; Giniunas, L.; Danielius, R.; İlday, Ömer Fatih200-fs 2.5-mJ pulses from a fiber-oscillator-seeded DPSS Yb:CaF2 MOPA are spectrally broadened in Ar and recompressed to 20 fs using a pair of LAK14 prisms. Multi-millijoule 12-fs pulses are feasible upon higher-order spectral phase correction.Item Open Access 3.5-W, 42-MHz, single-mode chirped pulse amplification fiber laser system at 1560 nm(OSA, 2017) Elahi, Parviz; Li, Huihui; İlday, Fatih ÖmerThere is much interest in the development of high power ultra-short fiber laser systems due to their significant properties and applications. Among them, Er-doped fiber lasers are showing more attention, especially in silicon processing and photovoltaic industries. Chirp pulse amplification (CPA) is the most common approach to establish high-power/high energy fiber lasers. Here, we demonstrate a CPA fiber laser system operating at 1560 nm. The system provides 3.5 W average output power at 42 MHZ pulse repetition rate corresponds to 83 nJ pulse energy. The laser system comprises a passively mode-locked oscillator and two amplifier stages, where the power amplifier is based on claddingpumped 10 μm-core EY co-doped fiber. The output pulses are compressible to 180 fs by using of two compressor gratings. The schematic of experimental setup is shown in Fig. 1(a). Seed source is a home-built dispersion-managed passively mode-locked oscillator delivering 5-ps long pulses at 42 MHZ repletion rate and 8 mW average power. We are using 70-cm long positive dispersion fiber (OFS, R2=56.7 fs2 /mm) after the gain fiber to manage group velocity dispersion delay (GDD) of the cavity and achieve broad spectrum. The output from oscillator delivers to stretch fiber including a 10-m long fiber (OFS). 30-ps long pulses after that delivers to the first stage amplifier, which consists of 1-m long Er 80-4/125 (CorActive) pumped by a single-mode diode laser at 976 nm via a wavelength-division-multiplexer (WDM). The first stage amplifier generates 120 mW of average power. The power amplifier is based on 1.4-m long Er-Yb co-doped fiber with 10 μm core and 128 μm cladding diameter. The pump source is a 16-W wavelength-stabilized diode laser at 976 nm. The pump and signal are combined with a multimode pump signal combiner (MPC). A 10/128 fiber pigtailed collimator is used to collimate output beam.Item Open Access 3.5-W, femtosecond chirped pulse amplification fiber laser system at 1560 nm(IEEE, 2017) Elahi, Parviz; Li, Huihui; İlday, Fatih ÖmerWe report a single-mode, 42 MHz, 3.5-W average power chirped pulse amplification fiber laser system operating at 1560 nm. The laser system comprises a dispersion-managed mode-locked oscillator and twoamplifier stages. The output pulses are compressed to 180 fs by using two diffraction gratings.Item Open Access 30-fs 1.6 mJ pulses at a kHz repetition rate from a single stage DPSS Yb amplifier(OSA, 2010) Andriukaitis, G.; Kartashov, D.; Pugzlys, A.; Lorenc, D.; Baltuska, A.; Giniunas, L.; Danielius, R.; İlday, Ömer Fatih200-fs 2.5-mJ pulses from a cw-diode-pumped Yb:CaF2 MOPA are spectrally broadened in Ar and recompressed to 30 fs at 980 nm using a prism pair. Multi-millijoule 12-fs pulses are feasible upon higher-order spectral phase correction.Item Open Access 33-fs Yb-fiber laser comb locked to Cs-atomic clock(IEEE, 2013) Şenel, Çağrı; Hamid, R.; Erdoğan, C.; Çelik, M.; Kara, O.; İlday, Fatih ÖmerDespite the prevalence of fiber frequency combs around 1.5 μm, few fully stabilized frequency combs have been demonstrated around 1.0 μm, despite the generally superior performance of Yb-fiber lasers compared to Er-fiber lasers. Short pulses are to generate coherent supercontinuum using anomalous dispersion regime of microstructured fibers. Near-zero cavity dispersion is highly desirable for low-noise frequency comb performance. Here, we report a Yb-doped fiber laser that operates at net-zero group-velocity dispersion and produces pulses that can be compressed externally to 33-fs. The frequency comb generated by this system is repetition-and carrier-envelope-phase-locked to Cs atomic clocks. The laser oscillator design is based on a novel algorithmic methodology, which allows us to design cavities to meet specific requirements; in this case, there was the need to generate as short pulses as possible, while having several nJ of pulse energy and the cavity at strictly zero total dispersion.Item Open Access 45 GHz bandwidth-efficiency resonant cavity enhanced ITO-Schottky photodiodes(OSA, 2001) Bıyıklı, Necmi; Kimukin, İbrahim; Aytür, Orhan; Özbay, Ekmel; Gökkavas, M.; Ünlü, M. S.We demonstrated high-performance resonant cavity enhanced ITO-Schottky photodiodes. We achieved a peak efficiency of 75% around 820 nm with a 3-dB bandwidth of 60 GHz resulting in a bandwidth-efficiency product of 45 GHz.Item Open Access 50-W, 1.6-GHz pulse repetition rate from a burst-mode Yb-doped fiber laser(IEEE, 2017) Elahi, Parviz; Ertek, A. C.; Eken, K.; İlday, Fatih ÖmerWe report a 50-W average power Yb-doped fiber laser amplifier system. The laser system produces bursts at a minimum rate of 200 kHz, with 1.6 GHz intraburst repetition rate. The total energy delivers in a burst is 250 μJ and the individual pulse energy is about 0.4 μJ. The output pulses are compressed to 270 fs by using two compressor gratings.Item Open Access 83 W, 1 ns, 3.1 MHz all-fiber laser for micromachining(IEEE, 2011) Özgören, Kıvanç; Öktem, Bülent; Yılmaz, Sinem; İlday, F. Ömer; Pasin, E.; Eken, K.Fiber lasers are commonly used for various material processing applications. The advantages (such as simplicity of the system, high material removal rate) and disadvantages (larger heat-affected zone, reduced precision) of nanosecond pulses over sub-picosecond pulses are well known. © 2011 IEEE.Item Open Access 94.8 km-range direct detection fiber optic distributed acoustic sensor(Optical Society of America(OSA), 2019) Uyar, Faruk; Uyar, Talha; Ünal, Canberk; Kartaloğlu, Tolga; Özdur, İbrahim; Özbay, EkmelThis work demonstrates an ultra-long range direct detection fiber optic distributed acoustic sensor which can detect vibrations at a distance of 94.8 km with 10 m resolution along the sensing fiber.Item Open Access ABC: a double-conversion compiler/solver for nanoscience calculus(Computational Publications, 2003) Kulik, Igor O."CompLab" ("Compiler Laboratory") or "ABC" ("Advanced Basic-C") is a double conversion compiler working in two parallel regimes (A and B) one of which is similar to that of MATLAB while the other is a professional compilation routine similar to C and FORTRAN languages. Double-conversion scheme of compilation allows making advantage of both the simplicity of used code (program, commands) and at the same time of the power of C language in speed and in the capacity of CPU memory usage. The "A" regime allows for on-line calculation of multidimensional integrals, eigenvalues of large matrices, roots of nonlinear equations, plotting functions and their derivatives, etc. The "B" regime is an exportable program of conversion from the pseudobasic input code to C-code, compilation and solution. The C-code is fit for usage in any computational platform including Windows, OS/2, Linux and Unix machines.Item Open Access Ablation-cooled material removal at high speed with femtosecond pulse bursts(OSA, 2015) Kerse, Can; Kalaycıoğlu, Hamit; Elahi, Parviz; Akçaalan, Önder; Yavaş, S.; Aşık, M. D.; Kesim, Deniz Koray; Yavuz, Koray; Çetin, Barbaros; İlday, Fatih ÖmerWe report exploitation of ablation cooling, a concept well-known in rocket design, to remove materials, including metals, silicon, hard and soft tissue. Exciting possibilities include ablation using sub-microjoule pulses with efficiencies of 100-mJ pulses.Item Open Access Active matter alters the growth dynamics of coffee rings(OSA, 2018) Callegari, Agnese; Andaç, Tuğba; Weigmann, Pascal; Velu, Sabareesh K. P.; Pinçe, Erçağ; Volpe, G.; Volpe, GiovanniWe show that bacterial mobility starts playing a major role in determining the growth dynamics of the edge of drying droplets, as the droplet evaporation rate slows down.Item Open Access AlGaN quadruple-band photodetectors(IEEE, 2009) Gökkavas, Mutlu; Bütün, Serkan; Caban, P.; Strupinski, W.; Özbay, EkmelQuadruple back-illuminated ultraviolet metal-semiconductor-metal photodetectors with four different spectral responsivity bands were demonstrated. The average of the full-width at half-maximum (FWHM) of the quantum efficiency peaks was 9.98 nm.Item Open Access All-chalcogenide variable infrared filter(SPIE, 2009) Kondakcı, H. Esat; Köyle, Özlem; Yaman, Mecit; Dana, Aykutlu; Bayındır, MehmetWe present the design, fabrication, characterization of spatially variable infrared filter and a demonstration of the filter as a simple infrared spectrometer. A varying photonic band gap filter which consists of thermally evaporated, high refractive index contrast amorphous chalcogenide glass multilayers, makes the structure suitable to be used as spectrometer. Due to graded thickness structure, the filter exhibits a position dependent stop band and a cavity mode ranging from 2 to 8 μm wavelengths. It is demonstrated that the filter can be used to detect absorption peaks of common gases in the cavity mode range of the filter. © 2009 SPIE.Item Open Access All-fiber burst mode femtosecond laser system integrated with OCT for cataract surgery(IEEE, 2015) Kesim, Denizhan Koray; Kalaycıoglu, Hamit; Kerse, Can; İlday, F. ÖmerCataract condition is responsible for two thirds of preventable visual impairments afflicting nearly 190 million all over the world [1]. Every year, 19 million cataract surgeries are performed worldwide [2]. Femtosecond laser-assisted cataract surgery has entered clinical use in recent years as an efficient and safe alternative to the traditional method. However, this laser-assisted surgery is in its infancy period and would benefit from lower pulse energies (to minimize collateral effects), shorter operation durations, and more compact laser systems. Fiber lasers can address these requirements with their robustness, compact size and minimal-alignment requiring structure. Further, burst mode operation [3], where high repetition rate pulses are delivered in packets repeated at a relatively low rate, have been shown to produce efficient ablation with minimal collateral thermal effects [4]. Here, we demonstrate the first fiber based burst-mode femtosecond laser device for cataract surgery. The laser is coupled to an optical coherence tomography (OCT) system with computerized controls (Fig. 1(a)). A home built all fiber Yb laser amplifier is seeded by a 109-MHz fiber oscillator, followed by a double-clad preamplifier, acusto optic modulator (AOM) pulse picker and a double-clad power amplifier. An FPGA based electronic system triggered by the oscillator is used to impose the desired pulse train on the laser beam. The system is able to produce pulses in the 5-10 µJ range compressible to sub-500 fs. The imaging and tissue processing functions are executed with OCT monitoring, using its galvo scanner and a common beam path. Maximum imaging depth is 1.6 mm with 8 µm axial resolution. The galvo scanner can reach a scan speed of 1 m/s with any desired scanning pattern. In our preliminary experiments, bursts comprising of 8 pulses with 3 µJ per pulse at 50 kHz burst repetition rate were applied to agar jells (Fig. 1 (b)), which have optical response similar to that of the cornea, as well as cornea obtained from cow eyes. Smooth cuts on ex vivo cow cornea by raster scan pattern with 70% overlapping spots (Fig 1. (c)) and on agar jells with non-overlapping spots pattern (Fig 1. (d)) were obtained. Agar and ex vivo cow eye trials show that we can create incisions with different patterns below the surface, in addition to dotted patterns for corneal incision and smooth lines for capsulorhexis.