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Temperature profile and transient response of thermally tunable ridge waveguides with laterally supported suspension
摘要： Using the thermoreflectance imaging method, the temperature profile and transient response of thermally tunable ridge waveguides with laterally supported suspension are investigated. This method has a high accuracy in the temperature measurement. The experimental data convincingly confirm a uniform temperature distribution along the waveguide except the initial 30 μm long sections near the two longitudinal edges. The 10%–90% rising time and 90%–10% falling time of the device transient thermal response are also measured to be ≈48 μs and ≈44 μs, respectively, regardless of different waveguide lengths and at different heating powers. In addition, the delay time of the waveguide transient thermal response is revealed to be 1.3 μs by comparison between experiment and simulation.
关键词： thermally tunable ridge waveguides,thermoreflectance imaging,temperature profile,transient response
更新于2025-09-19 17:13:59
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Diamond-blade diced trapezoidal ridge waveguides in YCOB crystal for second harmonic generation
摘要： Trapezoidal ridge waveguides have been fabricated in YCOB nonlinear optical crystals by carbon ion irradiation and precise diamond-blade dicing. The diced ridges with smooth side-walls allow for near-infrared (1064 nm) light guiding with propagation losses around 1 dB/cm. Refractive index pro?le of a waveguide has been re- constructed in a reasonable manner. Green second harmonic light have been generated at room temperature via type I birefringent phase matching. Under the pump of continuous and pulsed lasers, conversion e?ciencies for guided-wave frequency doubling can be up to ~1.10% W ?1 and ~6.22%, respectively.
关键词： SHG,Trapezoidal ridge waveguides,YCOB crystal
更新于2025-09-19 17:13:59
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[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) - Zn:MgO:PPLN Waveguides for Rb Cold Atom Trap Based Quantum Gravitometry in a CubeSat
摘要： Satellite based experiments require laser systems that are compact and efficient, which are robust against vibration, radiation and thermal cycling. Supported by Innovate UK’s Quantum Technology ‘Cold Atom Space PAyload (CASPA)’ project we have fabricated PPLN (Periodically Poled Lithium Niobate) ridge waveguides to act as efficient frequency converters for rubidium atom cooling via second harmonic generation (SHG) of telecoms lasers. CASPA is a technology demonstrator for magneto-optical cooling within a micro CubeSat laying the foundations for novel gravitometry and global positioning techniques. With respect to the particular environment of operation we have developed single mode ridge waveguides with metal indiffusion and dicing. We fabricate PPLN ridge waveguides by firstly high-voltage poling of z-cut magnesium doped lithium niobate, then deposit and thermally indiffuse Zn to create planar optical confinement, followed by ultra-precision ductile dicing to define ridge waveguides and coupling facets. Our non-AR coated waveguides have produced optical to optical efficiencies of up to 22.0 %, producing 44.7 mW of SHG with 203 mW of transmitted pump. The 2nd moment MFD was calculated to be 10.8 and 10.0 μm in the x and y axes, respectively, allowing efficient mode matching to standard telecommunication fibre. With a free space launch we have measured an average insertion loss, over multiple dies, of -1.3 dB, for 4 cm long waveguides that are non-AR coated. When comparing to other ridge PPLN waveguides this is a 3.7 dB improvement over competing examples of a 5 cm bonded and thinned device and a 1.9 dB improvement for a 1 cm proton exchange device. These low insertion losses can be attributed to both the symmetric pump mode of the waveguides enabling efficient mode matching and low amounts of optical scattering from waveguide sidewall roughness. We have shown ductile dicing to produce an average surface roughness of 0.29 nm (Sa) on waveguide facets in a single processing step.
关键词： CubeSat,rubidium atom cooling,second harmonic generation,ridge waveguides,PPLN
更新于2025-09-16 10:30:52
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[IEEE 2019 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM) - Boulder, CO, USA (2019.1.9-2019.1.12)] 2019 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM) - Frozen-Light Modes in 3-way Coupled Silicon Ridge Waveguides
摘要： Frozen-light modes supported by the stationary inflection point (SIP) within the pass band of 3-way coupled periodic silicon ridge waveguides is demonstrated. Precise tuning of the coupling between forward and backward propagating modes lead to mode degeneracy with vanishing group velocity. The unit cell is tuned to obtain the SIP on the third branch in the dispersion diagram. Subsequently, we demonstrate a finite structure with 23 unit cells to support the frozen mode at the SIP frequency. For this example, the group velocity at the SIP is 385 times slower than speed of light in vacuum. Transmission resonances of the finite structure, as well as the field distribution within the device at the SIP frequency are studied and presented.
关键词： Frozen-light modes,group velocity,dispersion engineering,3-way coupled periodic silicon ridge waveguides,stationary inflection point
更新于2025-09-16 10:30:52
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Design of a Compact 3D Metal Printed Ka-band Waveguide Polarizer
摘要： This letter presents design, development and characterization of compact wide band 3D printed circular waveguide based polarizer operating in Ka-band (28-34 GHz). The polarizer structure is investigated using fundamental and higher order modes and based on which a simplified equivalent structure is derived giving physical insight into its mechanism of operation. The design consists of a pair of radially opposite grooves inside a circular waveguide and excited using a coaxial probe which makes the design simple and highly compact as compared to other conventional circular polarizers. The design is compared with other existing waveguide based polarizers in terms of electrical and physical parameters. Fabrication is done using high resolution direct metal aluminum 3D metal printing. The measured axial ratio is better than 3 dB over the frequency band. The design simplicity makes it attractive for application in millimeter wave frequencies and beyond.
关键词： polarizers,septum,waveguide,ridge waveguides,groove,Circular polarization
更新于2025-09-11 14:15:04