A neodymium (Nd) doped lithium-niobate-on-insulator (LNOI) was fabricated from a lithium niobate (LN) substrate diffusion-doped with Nd prior to the LNOI fabrication process. Diffusion doping enables the fabrication of differently doped regions on a single LNOI substrate, a key advantage for future applications in highly integrated photonics. Fluorescence spectra, emission cross-section, fluorescence lifetime, and small-signal gain of Nd:LNOI were determined for the first time to our knowledge and compared with data published for diffusion-doped ridge or channel waveguides in LN substrates. For an 11 mm-long sample, we achieve a small-signal gain for π (σ) polarization of about 14 (10) dB when pumping with a Ti:Sapphire laser, which is promising for future active components in Nd:LNOI like amplifiers and lasers.

We report on fabrication of ridge waveguides formed in congruent periodically poled lithium niobate substrates using annealed and reverse proton exchange followed by diamond blade dicing. 1 W of second-harmonic generation at 775 nm has been obtained in a single-pass in 50 mm long ridge waveguides with internal conversion efficiency of 70%. At this power level, 97% pump depletion has been reached. Although elevated temperature operation and ridge geometry help to mitigate photorefractive damage (PRD) effects, nevertheless, at even higher second harmonic outputs significant power drop with blue shift and distortion of the SHG tuning curve have been observed indicating an onset of PRD.

In this work, we report on an investigation of the ytterbium diffusion characteristics in lithium niobate. Ytterbium-doped substrates were prepared by in-diffusion of thin metallic layers coated onto x- and z-cut congruent substrates at different temperatures. The ytterbium profiles were investigated in detail by means of secondary neutral mass spectroscopy, optical microscopy, and optical spectroscopy. Diffusion from an infinite source was used to determine the solubility limit of ytterbium in lithium niobate as a function of temperature. The derived diffusion parameters are of importance for the development of active waveguide devices in ytterbium-doped lithium niobate.

The ferroelectric crystal lithium niobate (LiNbO 3 ) is an attractive material for a variety of photonics applications due to its excellent electro-optic and nonlinear properties. Another benefit of rare-earth doped LiNbO 3 is the easy implementation of low-loss waveguides leading to the development of waveguide amplifiers as well as waveguide lasers. In the past, a great deal of attention was attracted to the development of optically pumped Er 3+ - and Nd 3+ -doped LiNbO 3 waveguide lasers emitting around the 1.5 μm telecom wavelength range and 1.08 μm, respectively. Up to date, Er- and Nd-doped LiNbO 3 channel waveguide lasers with slope efficiencies up to 30 % [1] and 40 % [2], respectively, have been reported. However, a further improvement of the laser performance can be achieved by using a ridge waveguide geometry due to the smaller mode fields and improved overlap of modes at different wavelengths as well as the reduction of photorefractive damage.

We report on a miniature all-fiber dual parameter sensor capable of simultaneous measurement of the refractive index (RI) and temperature of fluids and gases. The high-sensitivity sensing element is comprised of two Fabry-Perot (FP) micro-resonators fabricated in a single-mode fiber and has a total length of <100  μm. The RI sensing cavity is formed by diamond blade dicing, whereas a thinner silicon inlay glued into it serves as a temperature sensor. The sensor's performance was tested on sucrose solutions over a range of temperatures. For the evaluation of the backreflected FP spectra, phase tracking of the characteristic Fourier transform components was used. Good accuracy (0.01°C) and linearity of temperature measurement with Si inlay with sensitivity 0.097 rad/°C (85.2 pm/°C) were found, whereas the open cavity allowed for reliable temperature-compensated measurements of 10-3 RI steps with 290 rad/RIU (1130 nm/RIU) sensitivity.

We demonstrate an optical self-accelerating state driven by nonlinear coherent interaction of its constituting components with opposite “mass-sign”. The coherent propulsion, highly immune to initial phase conditions, is surprisingly enhanced comparing to its incoherent counterpart. © 2019 The Author(s)

This paper provides a generic way to fabricate a high-index contrast tapered waveguide platform based on dielectric crystal bonded on glass for sensing applications. As a specific example, KLu(WO4)2 crystal on a glass platform is made by means of a three-technique combination. The methodology used is on-chip bonding, taper cutting with an ultra-precise dicing saw machine and inductively coupled plasma-reactive ion etching (ICP-RIE) as a post-processing step. The high quality tapered waveguides obtained show low surface roughness (25 nm at the top of the taper region), exhibiting propagation losses estimated to be about 3 dB/cm at 3.5 μm wavelength. A proof-of-concept with crystal-on-glass tapered waveguides was realized and used for chemical sensing.

Waveguide circuits play a key role in modern integrated optics and provide an appealing approach to scalability in quantum optics. We report on periodically poled ridge waveguides in z-cut potassium titanyl phosphate (KTiOPO4 or KTP), a material that has recently received growing interest due to its unique dispersion properties. Ridges were defined in surface-near rubidium-exchanged KTP by use of a precise diamond-blade dicing saw. We fabricated single-mode ridge waveguides at around 800 nm which exhibit widths of 1.9-3.2 μm and facilitated type-II second harmonic generation from 792 nm to 396 nm with high efficiency of 6.6 %/W·cm2. Temperature dependence of the second harmonic process was found to be 53 pm/K. The low temperature dependence and high nonlinear conversion efficiency make our waveguides ideally suited for future operations in classical nonlinear integrated optics and integrated quantum networking applications.

Erbium-ytterbium-codoped titanium in-diffused ridge waveguides optical amplifiers in x-cut congruent LiNbO3 substrates pumped at 980.5 rim and 1486 rim are reported for the first time. An internal gain of 2.8 dB/cm has been measured in 2.3 cm long Yb:Er:Ti:LiNbO3 ridge waveguides for the coupled pump power of 145 mW at 980.5 rim, which is the highest gain ever reported. to the best of our knowledge, for erbium-based LiNbO3 waveguide amplifiers under 980 nm excitation. Furthermore, we realized an internal gain of 3.2 dB/cm for the coupled pump power of 200 mW at 1486 nm, which also exceeds the best literature values for Er:Ti:LiNbO3 waveguide amplifiers pumped at this wavelength. In addition, we report on a method for local periodic poling (periods of 30 mu m and 18.4 mu m) of ridge waveguides in LiNbO3, which allows for future integration of waveguide lasers and nonlinear frequency converters on the same substrate.

We report on the fabrication and characterization of ridge waveguides in z-cut KTiOPO4 fabricated by Rb-ion exchange and subsequent precise diamond-blade dicing. Low attenuation values of 1.3 dB/cm (1.6 dB/cm) were determined at a wavelength of 1550 nm for TE (TM) polarization. Surface quality obtained by dicing is excellent for side walls of diced ridges and prepared end faces used for light coupling. The dispersion characteristics of the waveguides are determined and the results are compared to simulations. Finally, the nonlinear performance of the ridges is demonstrated by second harmonic generation of similar to 1060 nm pump light. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

We discuss results on a novel fabrication scheme for optical ridge waveguides in KTP by combination of ridge definition using a diamond blade dicing saw and Rb/Ba ion exchange. In contrast to conventional waveguides in KTP, our samples were prepared in substrates that have their z-axis lying in the surface plane, perpendicular to the waveguide. The ridge waveguides were ion-exchanged through their cut flanks followed by further annealing treatment in air. This results in a homogeneous refractive index increase across the rectangular waveguide cross section. Since Rb ions are only mobile along the z-axis, they cannot diffuse into the depth. Therefore, the fabricated waveguides can withstand elevated temperatures. We determined propagation losses to be only 0.3dB/cm (0.4dB/cm) for TE (TM) polarization at similar to 1060nm. These novel waveguides can allow for improved mode overlap in frequency conversion processes and better coupling of light from a fiber to the waveguide.

We report on characterization of ridge waveguides fabricated in KTP (KTiOPO4) by use of diamond-blade dicing and Rb/Ba ion exchange. The waveguides were prepared in substrates that have their z-axis in the surface plane, perpendicular to the waveguide direction. This hinders the RbBa ions from diffusion into the depth, as they are only mobile along the z-axis, and improves the waveguide's resistance against elevated temperature. Attenuation coefficients of 0.3 dB/cm (0.4 dB/cm) for TM (TE) polarization were measured at 1060 nm wavelength. Internal conversion efficiency of up to 3.3%/(W cm2) was determined for type-II SHG of 1064 nm.

We present continuous wave laser activity in neodymium-doped sapphire ridge waveguides. The ridges were prepared using diamond blade dicing of thin Nd3+: sapphire films grown on sapphire substrates by pulsed laser deposition. Lasing was realized at wavelengths of 1092 nm and 1097 nm for ridge waveguide orientations addressing the sigma- and pi-polarization, respectively. A maximum slope efficiency with respect to incident pump power of 12% was achieved in s- polarization with a ridge cross section of 40.8 x 2.6 mu m(2) and a ridge length of 8 mm. With an available incident pump power of 2.8 W from a Ti: sapphire laser, a maximum output power of 322 mW was realized. (C) 2017 Optical Society of America

We report on the fabrication of ridge waveguides in KTiOPO4 nonlinear optical crystals through carbon ion irradiation followed by precise diamond blade dicing. The diced side-walls have low roughness, which allows for low propagation loss of ~1dB/cm in fabricated of ridges. The waveguide property investigation has been performed at 1064 nm as well as 532 nm, showing good guidance at both TE and TM polarizations. Based on type II phase matching configuration, efficient second harmonic generation of green light at room temperature has been realized. High conversion efficiencies of ~1.12%W-1 and ~12.4% have been obtained for frequency doubling under the pump of continuous-wave (CW) and pulsed fundamental waves at 1064 nm, respectively.

We report on the fabrication and characterization of ridge waveguides in lithium niobate thin films by diamond blade dicing. The lithium niobate thin films with a thickness of 1 µm were fabricated by bonding a He-implanted lithium niobate wafer to a SiO(2)-coated lithium niobate wafer and crystal ion slicing. Propagation losses of 1.2 dB/cm for TE and 2.8 dB/cm for TM polarization were measured at 1550 nm for a 9.28 mm long and 2.1 µm wide waveguide using the Fabry-Perot method.

Electro-optical circuit boards should provide simple and cost-effective coupling techniques and crosstalk levels of less than -30  dB. A dicing saw was used to create waveguide grooves with a surface roughness of less than 183 nm in a 1.6-mm-thick polymethyl methacrylate polymer (PMMA) substrate. The buried optical waveguides were made from SU-8 in a PMMA substrate covered with a 1-mm PMMA sheet. The propagation loss for a 500  μm×570  μm straight waveguide was 0.9 dB/cm at 1310 nm. The coupling between parallel waveguides was measured at separation distances from 45 to 595 μm. The crosstalk was less than -40  dB for 65-mm-long waveguides. This fabrication method shows potential for dense optical interconnects with very low crosstalk.

Ridge waveguides have been fabricated in Nd:YAG crystals by using ion irradiation and precise diamond blade dicing. Continuous-wave lasers at similar to 1064 nm have been realized in the ridge waveguides through optical pumping at 808 nm at room temperature. The ridge guiding structure shows superior lasing performance with respect to the planar counterpart with a slope efficiency of 43% and a maximum output power of 84 mW. (C) 2013 Optical Society of America

We show, theoretically and experimentally, the existence of a multi-stable regime in a nonlinear saturable coupler. In spite of its simplicity, we found that this model shows generic and fundamental properties of extended saturable lattices. The study of this basic unit becomes crucial to understand localization mechanisms and dynamical properties of extended discrete nonlinear saturable systems. We theoretically predict the regions of existence of intermediate solutions, and experimentally confirm it by observing a multi-stable propagation regime in a LiNbO3 saturable coupler. This constitutes the first experimental evidence of the existence of these unstable symmetry-broken stationary solutions.

We observe theoretically and experimentally the phenomenon of spontaneous symmetry breaking of strongly localized nonlinear optical modes at the microwatt level in a one-dimensional photonic lattice with a single coupling defect.

The existence and stability of spatial solitons in one-dimensional binary photonic lattices with alternating spacing and a saturable defocusing type of nonlinearity are investigated. Five types of nonlinear localized structures are found to exist: two in the mini-gap in the energy spectrum and others in the regular gap. It is proved that some of them are stable in certain ranges of the system parameters. Interactions between two identical localized structures propagating parallel to each other are investigated, too. It is shown that this interaction leads to formation of different localized patterns, such as solitons, breather-like modes, and breather complexes. The interaction output depends on the power and type of interacting identical solitons, the separation between them, the width of the mini-gap, and the phase relation between the tails of interacting solitons.