Showing papers by "Fredrik Laurell published in 2016"

Terahertz parametric generation and amplification from potassium titanyl phosphate in comparison with lithium niobate and lithium tantalate

Abstract: We report superior terahertz parametric generation from potassium titanyl phosphate (KTP) over congruent-grown lithium niobate (CLN) and lithium tantalate (CLT) in terms of parametric gain and laser damage resistance Under the same pump and crystal configurations, the signal emerged first from KTP, 5% Mg-doped CLN, CLN, and then finally from CLT The signal growth rate in KTP was comparable to that in 5%-Mg-doped CLN, but the signal power from KTP reached a much higher value after all the other crystals were damaged by the pump laser We further demonstrate seeded terahertz parametric amplification in an edge-cut KTP at 574 THz The THz parametric amplifier (TPA) employs a 17-mm long KTP gain crystal, pumped by a passively Q-switched pump laser at 1064 nm and seeded by a continuous-wave diode laser tuned to the signal wavelength at 10862 nm With 58-mJ energy in a 520-ps pump pulse and 100-mW seed signal power, we measured 5-W peak-power THz output from the KTP TPA with 22% pump depletion In comparison, we measured no detectable THz output power from a similar edge-cut CLN TPA under the same pump power, detection scheme, and crystal configuration, when tuning the seed laser wavelength to 10722 nm and attempting to generate a radiation at 21 THz

Accurate modeling of high-repetition rate ultrashort pulse amplification in optical fibers.

Abstract: A numerical model for amplification of ultrashort pulses with high repetition rates in fiber amplifiers is presented. The pulse propagation is modeled by jointly solving the steady-state rate equations and the generalized nonlinear Schrodinger equation, which allows accurate treatment of nonlinear and dispersive effects whilst considering arbitrary spatial and spectral gain dependencies. Comparison of data acquired by using the developed model and experimental results prove to be in good agreement.

Periodic poling of Rb-doped KTiOPO 4 by coercive field engineering.

Abstract: We demonstrate fine-pitch periodic poling of bulk Rb-doped KTiOPO4 using a coercive field grating induced by ion-exchange. These samples were used for quasi phase matched (QPM) second harmonic generation at 795 nm with a normalized conversion efficiency of 1.7% W-1cm-1. Additionally, the ion-exchange introduced a refractive index change over the sample thickness resulting in a phasematching wavelength shift of 0.21 nm, adding extra tunability to the QPM device.

Waveguides in polycrystalline diamond for mid-IR sensing

Abstract: 8 mm long channel waveguides were manufactured in polycrystalline diamond with inductively coupled plasma etching and characterized in terms of mode-profile and propagation loss in the 1.5 – 3.4 μm spectral region. As proof of principle, the waveguides were evaluated in an evanescent field sensing setup targeting the CH absorption peak of isopropanol at ~3.4 μm, showing good agreement with numerical finite element simulations.

All-Fiber Nanosecond Gating for Time-Resolved Spectral Analysis

Abstract: We demonstrate the addition of time gating to a standard optical spectrum analyzer (OSA) operating in the spectral region $\sim 1.06~\mu \text{m}$ . This is accomplished by opening for 7 ns the optical input to the OSA with an electrically driven poled fiber in a Sagnac loop. The sequential interrogation with nanosecond resolution of the reflection from three fiber Bragg gratings along a piece of fiber allows distinguishing the spectral peaks created with a minimum separation of 85 cm. The passive extinction ratio of this device is >40 dB and returns to >40 dB from >23 dB on a 35-ns time scale directly after time gating.

High-aspect ratio microchannels fabricated in fused silica hollow fibres using Tesla coil

Abstract: A novel method to fabricate microchannels into fused silica capillaries and hollow fibres by a high-voltage high-frequency corona discharge induced by a Tesla coil is demonstrated. Channels as narrow as 2.2 μm are successfully made in capillaries with 2 μm inner and 125 µm outer diameters.

Multiwavelength laser designed for single-frame digital holography.

Abstract: In this paper, we present a tailored multiwavelength Yb-fiber laser source in the 1.03 μm spectral region for spatially multiplexed digital holographic acquisitions. The wavelengths with bandwidths below 0.1 nm were spectrally separated by approximately 1 nm by employing fiber Bragg gratings for spectral control. As a proof of concept, the shape of a cylindrically shaped object with a diameter of 48 mm was measured. The holographic acquisition was performed in single-shot dual-wavelength mode with a synthetic wavelength of 1.1 mm, and the accuracy was estimated to be 3% of the synthetic wavelength.

Terahertz parametric amplification using KTiOPO4

Abstract: We show superior terahertz parametric generation from potassium titanyl phosphate over lithium niobate and lithium tantalate, and demonstrate seeded parametric amplification in KTP with a ~5W peak output power at 5.7 THz.

Ion-exchange induced coercive field gratings for QPM devices in RB-doped KTP

Abstract: We demonstrate 3.16μm periodic poling in RKTP using a coercive field grating induced by ion-exchange. The process results in a linear refractive index change over the sample thickness, adding extra tunability to the QPM device.

Terahertz parametric amplification using KTiOPO 4

Abstract: We show superior terahertz parametric generation from potassium titanyl phosphate over lithium niobate and lithium tantalate, and demonstrate seeded terahertz parametric amplification in KTP at 5.7 THz.

Numerical study and validation of ultra-short pulse amplification in fiber amplifiers at high repetition rates

Abstract: We present a numerical method for studying fiber-based ultra-short pulse amplification at high repetition rates. Validation of the simulations, by comparison with experimental results, are also presented.