Huseyin Cankaya | Deutsche Elektronen-Synchrotron (original) (raw)

Papers by Huseyin Cankaya

Optics Express

We report, what is to our knowledge, the highest average power obtained directly from a Yb:YLF re... more We report, what is to our knowledge, the highest average power obtained directly from a Yb:YLF regenerative amplifier to date. A fiber front-end provided seed pulses with an energy of 10 nJ and stretched pulsewidth of around 1 ns. The bow-tie type Yb:YLF ring amplifier was pulse pumped by a kW power 960 nm fiber coupled diode-module. By employing a pump spot diameter of 2.1 mm, we could generate 20-mJ pulses at repetition rates between 1 Hz and 3.5 kHz, 10 mJ pulses at 5 kHz, 6.5 mJ pulses at 7.5 kHz and 5 mJ pulses at 10 kHz. The highest average power (70 W) was obtained at 3.5 kHz operation, at an absorbed pump power level of 460 W, corresponding to a conversion efficiency of 15.2%. Despite operating in the unsaturated regime, usage of a very stable seed source limited the power fluctuations below 2% rms in a 5 minute time interval. The output pulses were centered around 1018.6 nm with a FWHM bandwidth of 2.1 nm, and could be compressed to below 1-ps pulse duration. The output beam maintained a TEM 00 beam profile at all power levels, and possesses a beam quality factor better than 1.05 in both axis. The relatively narrow bandwidth of the current seed source and the moderate gain available from the single Yb:YLF crystal was the main limiting factor in this initial study.

OSA Continuum

We report 190-mJ pulses with spectral content supporting sub-ps pulse-duration at a 10 Hz repetit... more We report 190-mJ pulses with spectral content supporting sub-ps pulse-duration at a 10 Hz repetition rate generated by a cryogenically-cooled, bulk Yb:YLF laser amplifier system. The amplifier system relies on a chirped pulse amplification architecture and consists of a fiber front-end, a regenerative amplifier, and two 4-pass amplifiers. The fiber front-end delivers 15-nJ, 1-ns stretched seed pulses, which are first amplified to 13-mJ pulse energy inside a Yb:YLF regenerative amplifier. Then the pulses are boosted further to 115 mJ and 190 mJ in two consecutive 4-pass amplifiers. To our knowledge, these are the highest pulse energies reported from Yb:YLF based amplifiers to date. We foresee shortening the pulsewidths to sub-400-fs range in future studies.

Optics Express

We present, what is to our knowledge, the first detailed lasing investigation of cryogenic Yb:YLF... more We present, what is to our knowledge, the first detailed lasing investigation of cryogenic Yb:YLF gain media in the E//a-axis. Compared to the usually employed E//c-axis, the a-axis of Yb:YLF provides a much broader and smooth gain profile, but this comes at the expense of reduced gain product. We have shown that, despite the lower gain, which (i) increases susceptibility to cavity losses, (ii) raises lasing threshold, and (iii) inflates thermal load, efficient and high-power lasing could be achieved in the E//a axis as well. A record continuous-wave (cw) powers above 300 W, cw slope efficiencies of 73%, and a tuning range covering the 995-1020.5 nm region were demonstrated. In quasi-cw lasing experiments, via minimization of thermal effects, slope efficiencies can be scaled up to 85%. In gain-switched operation, sub-50-µs long pulses with a peak power exceeding 2.5 kW at multi-kHz repetition rate were attained. We measured a beam quality factor below 1.5 for laser average powers up to 100 W and below 3 for laser average powers up to 300 W. Power scaling limits due to thermal effects, laser dynamics in pulsed pumping, and multicolor lasing operation potential were also investigated. The detailed results presented in this manuscript will pave the way towards development of high-power and high-energy Yb:YLF oscillators and amplifiers with sub-500-fs pulse duration.

EPJ Web of Conferences

We present a segmented THz based device (STEAM) capable of performing multiple high-field operati... more We present a segmented THz based device (STEAM) capable of performing multiple high-field operations on the 6D-phase-space of ultrashort electron bunches. With this single device, powered by few-micro-Joule, single-cycle, 0.3 THz pulses, we demonstrate record THz-acceleration of >30 keV, streaking with <10 fs resolution, focusing with >2 kT/m strength, compression to ~100 fs. The STEAM device can be fabricated with regular mechanical machining tools and supports real-time switching between different modes of operation. It paves the way for the development of THz-based compact electron guns, accelerators, ultrafast electron diffractometers and Free-Electron Lasers.

Applied Sciences

We performed a comparative spectroscopic analysis on three novel Tm 3+ :tellurite-based glasses w... more We performed a comparative spectroscopic analysis on three novel Tm 3+ :tellurite-based glasses with the following compositions Tm 2 O 3 :TeO 2-ZnO (TeZnTm), Tm 2 O 3 :TeO 2-Nb 2 O 5 (TeNbTm), and Tm 3+ :TeO 2-K 2 O-Nb 2 O 5 (TeNbKTm), primarily for 2-µm laser applications. Tellurite glasses were prepared at different doping concentrations in order to investigate the effect of Tm 3+ ion concentration as well as host composition on the stimulated emission cross sections and the luminescence quantum efficiencies. By performing Judd-Ofelt analysis, we determined the average radiative lifetimes of the 3 H 4 level to be 2.55 ± 0.07 ms, 2.76 ± 0.03 ms and 2.57 ± 0.20 ms for the TeZnTm, TeNbTm and TeNbKTm samples, respectively. We clearly observed the effect of the cross-relaxation, which becomes significant at higher Tm 2 O 3 concentrations, leading to the quenching of 1460-nm emission and enhancement of 1860-nm emission. Furthermore, with increasing Tm 2 O 3 concentrations, we observed a decrease in the fluorescence lifetimes as a result of the onset of non-radiative decay. For the 3 H 4 level, the highest obtained quantum efficiency was 32% for the samples with the lowest Tm 2 O 3 ion concentration. For the 1860-nm emission band, the average emission cross section was determined to measure around 6.33 ± 0.34 × 10 −21 cm 2 , revealing the potential of thulium-doped tellurite gain media for 2-µm laser applications in bulk and fiber configurations.

Nature photonics, 2018

Acceleration and manipulation of electron bunches underlie most electron and X-ray devices used f... more Acceleration and manipulation of electron bunches underlie most electron and X-ray devices used for ultrafast imaging and spectroscopy. New terahertz-driven concepts offer orders-of-magnitude improvements in field strengths, field gradients, laser synchronization and compactness relative to conventional radio-frequency devices, enabling shorter electron bunches and higher resolution with less infrastructure while maintaining high charge capacities (pC), repetition rates (kHz) and stability. We present a segmented terahertz electron accelerator and manipulator (STEAM) capable of performing multiple high-field operations on the 6D-phase-space of ultrashort electron bunches. With this single device, powered by few-micro-Joule, single-cycle, 0.3 THz pulses, we demonstrate record THz-acceleration of >30 keV, streaking with <10 fs resolution, focusing with >2 kT/m strength, compression to ~100 fs as well as real-time switching between these modes of operation. The STEAM device de...

2016 41st International Conference on Infrared, Millimeter, and Terahertz waves (IRMMW-THz), 2016

Lasers Congress 2016 (ASSL, LSC, LAC), 2016

Strong-field, single-cycle THz fields accelerate electrons with peak energies of up to 0.8 keV in... more Strong-field, single-cycle THz fields accelerate electrons with peak energies of up to 0.8 keV in an ultracompact THz gun with bunch charge of 45 fC. Energy spreads as low as 5.8% were also achieved.

Lasers Congress 2016 (ASSL, LSC, LAC), 2016

We present strong-field few-cycle 2-µm pulses based on air-filled Kagome-fiber compression of 140... more We present strong-field few-cycle 2-µm pulses based on air-filled Kagome-fiber compression of 140-µJ, 3.3-ps pulses from Ho:YLF amplifier to 48 fs and 11 µJ energy. This is the first demonstration of 70-fold compression from Kagome fibers at 2 µm.

Conference on Lasers and Electro-Optics, 2016

We demonstrate experimentally the onset of cascaded optical parametric amplification (COPA) in pe... more We demonstrate experimentally the onset of cascaded optical parametric amplification (COPA) in periodically-poled lithium niobate. This technique permits narrowband terahertz wave generation beyond the Manley-Rowe limit.

Conference on Lasers and Electro-Optics, 2016

Laser Phys, 2009

Abstract We report on the development of an extended-cavity, low-threshold femtosecond Cr 4+: for... more Abstract We report on the development of an extended-cavity, low-threshold femtosecond Cr 4+: forsterite laser operating near 1270 nm. The resonator was end-pumped by a continuous-wave Yb-fiber laser at 1060 nm. The 195-MHz short cavity could be operated with absorbed threshold pump powers as low as about 300 mW. To scale up the pulse energy, the cavity length was increased by using a q-preserving multipass cavity (MPC) consisting of a flat and a curved (R= 4 m), notched high-reflector. Kerr-lens mode locking was used to generate ...

Appl Phys B Lasers Opt, 2010

High-energy femtosecond lasers can be used in many applications such as micro machining, nonlinea... more High-energy femtosecond lasers can be used in many applications such as micro machining, nonlinear frequency conversion, and biomedical imaging. Although a cavity dumper or an external amplifier can be employed to increase the pulse energy of the laser, this ...

Page 1. Efficient low-threshold multipass-cavity femtosecond Cr 4+ :forsterite laser Huseyin Cank... more Page 1. Efficient low-threshold multipass-cavity femtosecond Cr 4+ :forsterite laser Huseyin Cankaya1, James G. Fujimoto2, and Alphan Sennaroglu1,3 1Laser Research Laboratory, Department of Physics, Koç University Rumelifeneri, Sariyer, Istanbul 34450, Turkey 2Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 3Corresponding Author, e-mail: asennar@ku.edu.tr ...

II. EXPERIMENTAL The tellurite glass sample was prepared with the composition of Nd3+:(0.8)TeO2-(... more II. EXPERIMENTAL The tellurite glass sample was prepared with the composition of Nd3+:(0.8)TeO2-(0.2)WO3 by melting the powder mixtures of Nd2O3 (99.9% purity), TeO2 (99.999% purity), and WO3 (99% purity). The batch containing 0.5 mole of Nd2O3 to 100 moles of (0.8)TeO2-(0.2)WO3 was melted in a platinum crucible at 800 ºC for 1 hour in ambient air atmosphere. The batch was then rapidly quenched in a preheated stainless steal mold below the glass transition temperature. Sample surfaces were polished to a thickness of 4.1 mm, ...

Laser physics, Feb 1, 2009

We report on the development of an extended-cavity, low-threshold femtosecond Cr 4+: forsterite l... more We report on the development of an extended-cavity, low-threshold femtosecond Cr 4+: forsterite laser operating near 1270 nm. The resonator was end-pumped by a continuous-wave Yb-fiber laser at 1060 nm. The 195-MHz short cavity could be operated with absorbed threshold pump powers as low as about 300 mW. To scale up the pulse energy, the cavity length was increased by using a q-preserving multipass cavity (MPC) consisting of a flat and a curved (R= 4 m), notched high-reflector. Kerr-lens mode locking was used to generate ...

Optics Express

We report, what is to our knowledge, the highest average power obtained directly from a Yb:YLF re... more We report, what is to our knowledge, the highest average power obtained directly from a Yb:YLF regenerative amplifier to date. A fiber front-end provided seed pulses with an energy of 10 nJ and stretched pulsewidth of around 1 ns. The bow-tie type Yb:YLF ring amplifier was pulse pumped by a kW power 960 nm fiber coupled diode-module. By employing a pump spot diameter of 2.1 mm, we could generate 20-mJ pulses at repetition rates between 1 Hz and 3.5 kHz, 10 mJ pulses at 5 kHz, 6.5 mJ pulses at 7.5 kHz and 5 mJ pulses at 10 kHz. The highest average power (70 W) was obtained at 3.5 kHz operation, at an absorbed pump power level of 460 W, corresponding to a conversion efficiency of 15.2%. Despite operating in the unsaturated regime, usage of a very stable seed source limited the power fluctuations below 2% rms in a 5 minute time interval. The output pulses were centered around 1018.6 nm with a FWHM bandwidth of 2.1 nm, and could be compressed to below 1-ps pulse duration. The output beam maintained a TEM 00 beam profile at all power levels, and possesses a beam quality factor better than 1.05 in both axis. The relatively narrow bandwidth of the current seed source and the moderate gain available from the single Yb:YLF crystal was the main limiting factor in this initial study.

OSA Continuum

We report 190-mJ pulses with spectral content supporting sub-ps pulse-duration at a 10 Hz repetit... more We report 190-mJ pulses with spectral content supporting sub-ps pulse-duration at a 10 Hz repetition rate generated by a cryogenically-cooled, bulk Yb:YLF laser amplifier system. The amplifier system relies on a chirped pulse amplification architecture and consists of a fiber front-end, a regenerative amplifier, and two 4-pass amplifiers. The fiber front-end delivers 15-nJ, 1-ns stretched seed pulses, which are first amplified to 13-mJ pulse energy inside a Yb:YLF regenerative amplifier. Then the pulses are boosted further to 115 mJ and 190 mJ in two consecutive 4-pass amplifiers. To our knowledge, these are the highest pulse energies reported from Yb:YLF based amplifiers to date. We foresee shortening the pulsewidths to sub-400-fs range in future studies.

Optics Express

We present, what is to our knowledge, the first detailed lasing investigation of cryogenic Yb:YLF... more We present, what is to our knowledge, the first detailed lasing investigation of cryogenic Yb:YLF gain media in the E//a-axis. Compared to the usually employed E//c-axis, the a-axis of Yb:YLF provides a much broader and smooth gain profile, but this comes at the expense of reduced gain product. We have shown that, despite the lower gain, which (i) increases susceptibility to cavity losses, (ii) raises lasing threshold, and (iii) inflates thermal load, efficient and high-power lasing could be achieved in the E//a axis as well. A record continuous-wave (cw) powers above 300 W, cw slope efficiencies of 73%, and a tuning range covering the 995-1020.5 nm region were demonstrated. In quasi-cw lasing experiments, via minimization of thermal effects, slope efficiencies can be scaled up to 85%. In gain-switched operation, sub-50-µs long pulses with a peak power exceeding 2.5 kW at multi-kHz repetition rate were attained. We measured a beam quality factor below 1.5 for laser average powers up to 100 W and below 3 for laser average powers up to 300 W. Power scaling limits due to thermal effects, laser dynamics in pulsed pumping, and multicolor lasing operation potential were also investigated. The detailed results presented in this manuscript will pave the way towards development of high-power and high-energy Yb:YLF oscillators and amplifiers with sub-500-fs pulse duration.

EPJ Web of Conferences

We present a segmented THz based device (STEAM) capable of performing multiple high-field operati... more We present a segmented THz based device (STEAM) capable of performing multiple high-field operations on the 6D-phase-space of ultrashort electron bunches. With this single device, powered by few-micro-Joule, single-cycle, 0.3 THz pulses, we demonstrate record THz-acceleration of >30 keV, streaking with <10 fs resolution, focusing with >2 kT/m strength, compression to ~100 fs. The STEAM device can be fabricated with regular mechanical machining tools and supports real-time switching between different modes of operation. It paves the way for the development of THz-based compact electron guns, accelerators, ultrafast electron diffractometers and Free-Electron Lasers.

Applied Sciences

We performed a comparative spectroscopic analysis on three novel Tm 3+ :tellurite-based glasses w... more We performed a comparative spectroscopic analysis on three novel Tm 3+ :tellurite-based glasses with the following compositions Tm 2 O 3 :TeO 2-ZnO (TeZnTm), Tm 2 O 3 :TeO 2-Nb 2 O 5 (TeNbTm), and Tm 3+ :TeO 2-K 2 O-Nb 2 O 5 (TeNbKTm), primarily for 2-µm laser applications. Tellurite glasses were prepared at different doping concentrations in order to investigate the effect of Tm 3+ ion concentration as well as host composition on the stimulated emission cross sections and the luminescence quantum efficiencies. By performing Judd-Ofelt analysis, we determined the average radiative lifetimes of the 3 H 4 level to be 2.55 ± 0.07 ms, 2.76 ± 0.03 ms and 2.57 ± 0.20 ms for the TeZnTm, TeNbTm and TeNbKTm samples, respectively. We clearly observed the effect of the cross-relaxation, which becomes significant at higher Tm 2 O 3 concentrations, leading to the quenching of 1460-nm emission and enhancement of 1860-nm emission. Furthermore, with increasing Tm 2 O 3 concentrations, we observed a decrease in the fluorescence lifetimes as a result of the onset of non-radiative decay. For the 3 H 4 level, the highest obtained quantum efficiency was 32% for the samples with the lowest Tm 2 O 3 ion concentration. For the 1860-nm emission band, the average emission cross section was determined to measure around 6.33 ± 0.34 × 10 −21 cm 2 , revealing the potential of thulium-doped tellurite gain media for 2-µm laser applications in bulk and fiber configurations.

Nature photonics, 2018

Acceleration and manipulation of electron bunches underlie most electron and X-ray devices used f... more Acceleration and manipulation of electron bunches underlie most electron and X-ray devices used for ultrafast imaging and spectroscopy. New terahertz-driven concepts offer orders-of-magnitude improvements in field strengths, field gradients, laser synchronization and compactness relative to conventional radio-frequency devices, enabling shorter electron bunches and higher resolution with less infrastructure while maintaining high charge capacities (pC), repetition rates (kHz) and stability. We present a segmented terahertz electron accelerator and manipulator (STEAM) capable of performing multiple high-field operations on the 6D-phase-space of ultrashort electron bunches. With this single device, powered by few-micro-Joule, single-cycle, 0.3 THz pulses, we demonstrate record THz-acceleration of >30 keV, streaking with <10 fs resolution, focusing with >2 kT/m strength, compression to ~100 fs as well as real-time switching between these modes of operation. The STEAM device de...

2016 41st International Conference on Infrared, Millimeter, and Terahertz waves (IRMMW-THz), 2016

Lasers Congress 2016 (ASSL, LSC, LAC), 2016

Strong-field, single-cycle THz fields accelerate electrons with peak energies of up to 0.8 keV in... more Strong-field, single-cycle THz fields accelerate electrons with peak energies of up to 0.8 keV in an ultracompact THz gun with bunch charge of 45 fC. Energy spreads as low as 5.8% were also achieved.

Lasers Congress 2016 (ASSL, LSC, LAC), 2016

We present strong-field few-cycle 2-µm pulses based on air-filled Kagome-fiber compression of 140... more We present strong-field few-cycle 2-µm pulses based on air-filled Kagome-fiber compression of 140-µJ, 3.3-ps pulses from Ho:YLF amplifier to 48 fs and 11 µJ energy. This is the first demonstration of 70-fold compression from Kagome fibers at 2 µm.

Conference on Lasers and Electro-Optics, 2016

We demonstrate experimentally the onset of cascaded optical parametric amplification (COPA) in pe... more We demonstrate experimentally the onset of cascaded optical parametric amplification (COPA) in periodically-poled lithium niobate. This technique permits narrowband terahertz wave generation beyond the Manley-Rowe limit.

Conference on Lasers and Electro-Optics, 2016

Laser Phys, 2009

Abstract We report on the development of an extended-cavity, low-threshold femtosecond Cr 4+: for... more Abstract We report on the development of an extended-cavity, low-threshold femtosecond Cr 4+: forsterite laser operating near 1270 nm. The resonator was end-pumped by a continuous-wave Yb-fiber laser at 1060 nm. The 195-MHz short cavity could be operated with absorbed threshold pump powers as low as about 300 mW. To scale up the pulse energy, the cavity length was increased by using a q-preserving multipass cavity (MPC) consisting of a flat and a curved (R= 4 m), notched high-reflector. Kerr-lens mode locking was used to generate ...

Appl Phys B Lasers Opt, 2010

High-energy femtosecond lasers can be used in many applications such as micro machining, nonlinea... more High-energy femtosecond lasers can be used in many applications such as micro machining, nonlinear frequency conversion, and biomedical imaging. Although a cavity dumper or an external amplifier can be employed to increase the pulse energy of the laser, this ...

Page 1. Efficient low-threshold multipass-cavity femtosecond Cr 4+ :forsterite laser Huseyin Cank... more Page 1. Efficient low-threshold multipass-cavity femtosecond Cr 4+ :forsterite laser Huseyin Cankaya1, James G. Fujimoto2, and Alphan Sennaroglu1,3 1Laser Research Laboratory, Department of Physics, Koç University Rumelifeneri, Sariyer, Istanbul 34450, Turkey 2Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 3Corresponding Author, e-mail: asennar@ku.edu.tr ...

II. EXPERIMENTAL The tellurite glass sample was prepared with the composition of Nd3+:(0.8)TeO2-(... more II. EXPERIMENTAL The tellurite glass sample was prepared with the composition of Nd3+:(0.8)TeO2-(0.2)WO3 by melting the powder mixtures of Nd2O3 (99.9% purity), TeO2 (99.999% purity), and WO3 (99% purity). The batch containing 0.5 mole of Nd2O3 to 100 moles of (0.8)TeO2-(0.2)WO3 was melted in a platinum crucible at 800 ºC for 1 hour in ambient air atmosphere. The batch was then rapidly quenched in a preheated stainless steal mold below the glass transition temperature. Sample surfaces were polished to a thickness of 4.1 mm, ...

Laser physics, Feb 1, 2009

We report on the development of an extended-cavity, low-threshold femtosecond Cr 4+: forsterite l... more We report on the development of an extended-cavity, low-threshold femtosecond Cr 4+: forsterite laser operating near 1270 nm. The resonator was end-pumped by a continuous-wave Yb-fiber laser at 1060 nm. The 195-MHz short cavity could be operated with absorbed threshold pump powers as low as about 300 mW. To scale up the pulse energy, the cavity length was increased by using a q-preserving multipass cavity (MPC) consisting of a flat and a curved (R= 4 m), notched high-reflector. Kerr-lens mode locking was used to generate ...