- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Silicon photodetector for integrated lithium niobate photonics
摘要： We demonstrate the integration of an amorphous silicon photodetector with a thin film lithium niobate photonic platform operating in the visible wavelength range. We present the details of the design, fabrication, integration, and experimental characterization of this metal-semiconductor-metal photodetector that features a responsivity of 22 mA/W to 37 mA/W over the wide optical bandwidth spanning in the 635 nm–850 nm wavelength range.
关键词： lithium niobate,visible wavelength range,integration,photonics,silicon photodetector
更新于2025-09-12 10:27:22
-
Second harmonic microscopy of poled x-cut thin film lithium niobate: Understanding the contrast mechanism
摘要： Thin film lithium niobate has been of great interest recently, and an understanding of periodically poled thin films is crucial for both fundamental physics and device developments. Second-harmonic (SH) microscopy allows for the noninvasive visualization and analysis of ferroelectric domain structures and walls. While the technique is well understood in bulk lithium niobate, SH microscopy in thin films is largely influenced by interfacial reflections and resonant enhancements, which depend on film thicknesses and substrate materials. We present a comprehensive analysis of SH microscopy in x-cut lithium niobate thin films, based on a full three-dimensional focus calculation and accounting for interface reflections. We show that the dominant signal in backreflection originates from a copropagating phase-matched process observed through reflections, rather than direct detection of the counterpropagating signal as in bulk samples. We simulate the SH signatures of domain structures by a simple model of the domain wall as an extensionless transition from a ?χ(2) to a +χ(2) region. This allows us to explain the main observation of domain structures in the thin-film geometry, and, in particular, we show that the SH signal from thin poled films allows to unambiguously distinguish areas, which are completely or only partly inverted in depth.
关键词： lithium niobate,thin films,ferroelectric domain structures,Second-harmonic microscopy,nonlinear optics
更新于2025-09-12 10:27:22
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Additive Fiber Optic Probe Technology for Precise Trimming of High-Performance Lithium Niobate Photonic Integrated Circuits
摘要： Lithium Niobate (LN) is a basic material of integrated optics, for example for electro and acousto-optical modulators, switches, diffraction gratings, nonlinear optical wavelength converters and others [1]. LN based ion exchange or Ti-indiffused contact photolithographic techniques are established technologies, however, finite tolerance of optical elements could not respond some modern applications. For example, high-purity suppressed carrier synthesis or high extinction ratio pulse generation for precision measurement systems require additional active trimming electrodes [2] at the device and corresponding servo loop. Recently developed direct laser writing (DLW) of femtosecond/ultrafast laser pulses [3] can be employed to address the problem, but this method is problematic for mass production and suffer from high insertion loss in optical waveguides (typically ~1 dB/cm compared to <0.1 dB/cm for Ti in-diffused waveguides). We have proposed a method that combines low loss of Ti in-diffused technology and passive permanent trimming of DLW. Moreover, the implementation of the proposed technique is based on very cheap commercially available equipment that makes it very attractive. This is a micro-machining of a thin loading metal film on the top of a waveguide. It is based on dependence of plazmon polariton excitation efficiency on the thickness of metal film. Titanium loading film by thickness of 10 nm adds addition insertion losses (~ 1 dB/mm) and changes effective refractive index of the waveguide (~ 10-6(cid:121)10-5). The loading film was deposited in zones of the integrated optical chip which were most sensitive to its influence such as X-type direction coupler and Y-branch. The film thickness of several nanometres allows rather low laser intensity could be used for local ablation. The simple semiconductor pump laser (978 nm) for erbium doped fiber optic amplifier was used. The output fiber was exploited as a probe. The tip of the fiber was positioned close to the integrated optical chip surface. For laser power of 500 mW the intensity on the tip of the output single mode fiber was about 1 kW/mm2. The integrated optical chip was attached to a precise 3-axis translation stage that allowed flexible manipulation of the loading film micro-machining. Monitoring of optical signals (1550 nm) on the output of integrated optical chip provided possibilities on-line control of the trimming. To demonstrate the efficiency of the proposed method the adjustment of extinction ratio ER (relation of maximum transmitted optical power to its minimum) of Mach-Zehnder modulator was performed. ER is critically dependent on precise power balance in both arms of the interferometers. We demonstrate increase in ER in 17 dB (from 30 to 47 dB). Our findings can potentially be applied in modulators for quantum key distribution, precise sensing, high fidelity signal processing and others.
关键词： trimming,photonic integrated circuits,integrated optics,fiber optic probe,Lithium Niobate
更新于2025-09-12 10:27:22
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Electro-Optic Frequency Comb Generation in Lithium Niobate Whispering Gallery Mode Resonators
摘要： Optical frequency combs (OFCs) are light sources whose spectra consists of equally spaced frequency lines in the optical domain [1]. They have great potential for improving high-capacity data transfer, all-optical atomic clocks, spectroscopy, and high-precision measurements [2]. In contrast to the traditional third-order nonlinearity based OFC generation methods, we present a new approach which is based on second-order non-linear effects in a whispering gallery mode (WGM) resonator made of lithium niobate (LN) [3,4]. Our system is composed of a resonant hybrid structure comprising an optical LN disk resonator and a microwave copper cavity. The hybrid structure enables highly efficient nonlinear mixing of photons. In this scheme, two continuous waves, one in the optical domain ((cid:2033) = 193 THz) and another in the microwave region (Ω = 8.9 GHz) couple within a LN WGM resonator [5]. The second-order non-linearity of LN leads to frequency comb generation via cascaded symmetric sum and difference frequency generation [6]. In our experiment, the optical pump power is coupled into the WGM by using a standard prism coupling method that is based on frustrated total internal reflection (Fig. 1 (a)). The microwave power is coupled using a coaxial probe coupled attached to the 3-D copper cavity specifically designed to have the microwave cavity resonance to be equal to the optical free spectral range of the LN resonator, required for efficient phase matching. In addition, the cavity design also provides a very good spatial overlap between the microwave and optical modes by confining the microwave field to the rim of the LN disk. In our proof-of-concept experimental demonstration we observe a 1.6 THz long frequency comb centred around 193.5 THz more than180 comb lines by using only 20 dBm of microwave power. Compared to previously reported OFCs generation schemes, this method has two major advantages: inherent phase stability, and better power efficiency. The power efficiency when measured in terms of pi-voltage of the modulator is 25 times better than a commercial Thorlabs modulator.
关键词： second-order non-linearity,whispering gallery mode resonators,electro-optic frequency comb generation,Optical frequency combs,lithium niobate
更新于2025-09-12 10:27:22
-
Microscale Generation of Entangled Photons without Momentum Conservation
摘要： We report, for the first time, the observation of spontaneous parametric down-conversion (SPDC) free of phase matching (momentum conservation). We alleviate the need to conserve momentum by exploiting the position-momentum uncertainty relation and using a planar geometry source, a 6 μm thick layer of lithium niobate. Nonphase-matched SPDC opens up a new platform on which to investigate fundamental quantum effects but it also has practical applications. The ultrasmall thickness leads to a frequency spectrum an order of magnitude broader than that of phase-matched SPDC. The strong two-photon correlations are still preserved due to energy conservation. This results in ultrashort temporal correlation widths and huge frequency entanglement. The studies we make here can be considered as the initial steps into the emerging field of nonlinear quantum optics on the microscale and nanoscale.
关键词： quantum optics,spontaneous parametric down-conversion,phase matching,lithium niobate,frequency entanglement,momentum conservation
更新于2025-09-12 10:27:22
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Efficient Er and Nd:Ti:LiNbO <sub/>3</sub> Ridge Waveguide Lasers for the Development of Mid Infrared Sources
摘要： The ferroelectric crystal lithium niobate (LiNbO3) 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 LiNbO3 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 Er3+- and Nd3+-doped LiNbO3 waveguide lasers emitting around the 1.5 μm telecom wavelength range and 1.08 μm, respectively. Up to date, Er- and Nd-doped LiNbO3 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. In this work, we report on our novel fabrication method for the development of highly efficient Er: and Nd:Ti:LiNbO3 ridge waveguide amplifiers and lasers [3,4]. To improve the amplifier/laser performance a fabrication technique comprised of ridge definition by diamond blade dicing followed by three-side Er/Nd/Ti deposition and in-diffusion (Fig. 1a) was developed and refined allowing higher Er/Nd doping concentrations and overlap of Er/Nd diffusion profiles with guided modes. An internal gain of 3.0 dB/cm has been measured in 4.6 cm long Er:Ti:LiNbO3 ridge waveguides for a coupled pump power of 200 mW at 1486 nm [3]. Utilizing this high internal gain, we achieved efficient lasing with a slope efficiency of 33 % at 1561 nm (see Fig. 1b) [3]. Furthermore, we demonstrated a Nd:Ti:LiNbO3 ridge waveguide laser with a slope efficiency of 34 % at a wavelength of 1084.7 nm pumped by a Ti:Sapphire laser emitting at 814 nm (see Fig. 1b) [4]. Due to improved photorefractive damage resistance by indium tin oxide (ITO) coating we achieved stable laser operation with a maximum output power of 108 mW for a coupled pump power of 402 mW corresponding to an intensity of ~490 kW/cm2 [4]. Recently, a novel method to achieve local periodic poling of Ti-diffused ridge waveguides in zx-cut LiNbO3 has been demonstrated [5]. In contrast to previous approaches, this method for periodic poling allows an optimization of the ridge waveguide geometry for nonlinear optics applications such as quasi-phase-matched (QPM) difference frequency generation (DFG). The ability to develop highly efficient Er- and Nd-doped ridge waveguide lasers in LiNbO3 and to achieve local QPM allows for the development of efficient hybrid optical devices in the same ridge waveguide emitting in the mid-infrared suitable for applications such as gas sensing.
关键词： Nd-doped,ridge waveguide lasers,lithium niobate,photonics applications,Er-doped
更新于2025-09-11 14:15:04
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Spatial Akhmediev Breathers in Slab Waveguides
摘要： The analytical breather-solutions of the Nonlinear Schr¨odinger Equation (NLS) have been intensively studied and veri?ed experimentally in the time-space system of optical pulse propagation in ?bers. In space-space systems, i.e. in optical beam propagation breathers in ultra-fast nonlinear media have not been observed due to the breather’s in?nite background and a resulting extremely large power. In a lithium niobate slab waveguide with two second-harmonic (SH) resonances the resulting quasi-cubic cascaded quadratic nonlinearity provided together with the intrinsic cubic susceptibility enough nonlinearity for breather excitation at experimentally reachable powers. We could characterize the ?rst ultra-fast spatial-spatial optical breathers in a 5-cm-long titanium in diffused lithium niobate slab waveguide at power levels down to tens of kW. The guided fundamental wave (FW) TM0 ?lm mode at l=1.32mm is phase-matched for type-I SH generation to TE0 and TE1 SH modes at temperatures near 295 and 344C. With temperature tuning the phase-mismatch and the two effective cascaded nonlinearities were adjusted. For breather observation, we aimed for a large phase-mismatch with low SH levels such that the cascaded nonlinearity is quasi-cubic and the propagation is well approximated by the NLS and its breather solutions. A frequency-doubled Nd:YAG-pumped OPA with CW-seeding delivered 5-ps long pulses with up to 200kW peak power in the waveguide. With a cylindrical telescope the beam was transformed into a very wide elliptical beam to approximate the breather background. The beam was end-?re coupled into the FW TM0 mode. A variable few% of the beam were separated and coupled with a tilt and good overlap to the main beam into the waveguide to produce a spatial modulation of the input with adjustable period and modulation depth. A beam width of 1.5mm was large enough in the compromise between available beam power and in?nite beam width. A beam with a transverse modulation with periods between 130 to 300mm approximates a constant background with modulation well enough to trigger modulation instability that develops eventually into the breather. The FW and the SH output of the waveguide were imaged into cameras. By changing the power the breather moves along the waveguide and the whole breather can be sampled at the waveguide end during a power scan. Each sample is normalized to its total power. An example is shown in Fig.1. Fig.1(left) Measured breather, scanned at the waveguide output dependent on power. (right) Simulation of the measurement. The in?uence of deviations from ideal theory and real world conditions like ?nite beam width, damping, non-uniform phase-mismatch, pulsed input, and cascading instead of an exact cubic nonlinearity was investigated in simulations describing the experiment very well (see example in Fig.1). The new platform is very versatile. A wide parameter space of different nonlinearity, varying transverse breather period and input modulation depth was investigated. Higher-order breathers were observed (see the grow-ing maxima between the main peaks in Fig.1). The drastic temperature-dependent reduction of the power level for breather formation due to cascading was observed. The expected speci?c details of quadratic breathers like a SH following the FW was documented. The spatial breather spectra showed the expected triangular shape.
关键词： modulation instability,lithium niobate slab waveguide,Nonlinear Schr¨odinger Equation,cascaded quadratic nonlinearity,optical breathers
更新于2025-09-11 14:15:04
-
[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Generation of a Few Cycle Terahertz Pulse in Aperiodically Poled Lithium Niobate by Sequence of Pump Pulses
摘要： It is shown that chirped aperiodically poled lithium niobate crystal is capable to generate powerful THz pulses with controllable number of THz field oscillations (from nearly single- to multi-cycles), when it is pumped by sequence of femtosecond laser pulses with chirped delays between adjacent pulses. The peak electric field strength of about 0.3 MV/cm (for non-focused THz beam) is predicted if intensity of each pump pulse in the sequence is 20 GW/cm2.
关键词： Optical rectification,Aperiodically poled lithium niobate,Terahertz pulse,Femtosecond laser pulses
更新于2025-09-11 14:15:04
-
Low-threshold 4/5 octave-spanning mid-infrared frequency comb in a LiNbO3 microresonator
摘要： Mid-infrared (MIR) optical frequency combs (OFCs) are ideal light sources for precision metrology and can ?nd extensive applications, especially in molecular spectroscopy and gas detection. Here the generation of mode-locked MIR frequency comb in a LiNbO3 microring through optimized slot-waveguide design is proposed. Such microcomb can span over four-?fths of an octave (ranging from (cid:24)2810 nm to (cid:24)4630 nm) with pump power as low as 50 mW, which can be applied to the 2f -3f self-referencing for fully stabilization and helpful to monolithic integration of the whole system. Further investigations on complex dynamical processes for the microcomb generation suggest that the intracavity soliton drifting caused by the third-order dispersion could be compensated by the self-steepening effect as introducing an additional drift through proper dispersion tailoring. This work could facilitate the low-threshold broadband MIR frequency comb generation technique, as well as provide a way to realize more delicate control of soliton microcombs in both temporal and spectral domain.
关键词： mid-infrared,high-order dispersion,self-steepening,Lithium niobate,nonlinear optics
更新于2025-09-11 14:15:04
-
Design of Linear Block Code Encoder and Decoder Using Electro-optical and All-optical Units
摘要： In this paper novel designs for linear block code encoder and decoder using optical techniques have been proposed. The structures are designed and simulated using lithium niobate based Mach–Zehnder Interferometer (LN-MZI) and nonlinear material MEH-PPV [poly (2-methoxy-5-(28-ethylhexyloxy)-PPV)] (plasmonic) based MZI (P-MZI). The proposed LN-MZI designs offer attractive parameters such as high extinction ratio (> 35 dB) and low insertion loss (< 0.095 dB), while the proposed P-MZI designs possess a compact structure (3,020–12,375 μm2). An analytical comparison between the two design methodologies and other earlier proposed designs is presented. Each design is presented with a verified mathematical structure. Other performance parameters like contrast ratio and amplitude modulation have also been computed for the presented designs.
关键词： electro-optic,Pockel effect,Kerr effect,error detection,syndrome bits,plasmonic,Mach–Zehnder interferometer,lithium niobate,parity,linear block code
更新于2025-09-11 14:15:04