Cross Sections Of Ridges Research Articles

Performance evaluation of silicon-chip-based mid-infrared Kerr optical frequency combs with ridge cross section

We present a complementary metal-oxide-semiconductor (CMOS) compatible platform for on-chip frequency comb generation in the mid-infrared region based on a silicon-on-insulator (SOI) microring resonator with ridge cross section. Flat dispersion tailoring is performed with dispersion variation of 4.04 × 10−6 ps/nm/km by adjusting the geometry parameter and the low-loss SOI microring resonator with total quality factor (Q) up to 106 can be realized at wavelengths from 3.3 to 3.6 µm. Furthermore, the thresholdless frequency combs consisting of 50 comb lines spanning from 3.1 to 4.0 µm (over 900 nm) can be realized using SOI microring resonator with 50 mW pump power. Besides, the study shows that the frequency interval of the comb is related to the selection of the dual-pumped wavelength. The influences of the coupling coefficient and the radius of microring on the bandwidth of mid-infrared OFC are also investigated numerically which shows that remarkable enhancement of mid-infrared OFC bandwidth can reach 449 nm when the coupling coefficient varies from 0.012 to 0.05. This research work is instructive for realizing highly integrated photonics and achieving the experimental generation of mid-infrared optical frequency combs, which could enable substantial progress in spectroscopy applications.

ТОРОСЫ ПРОЛИВА ШОКАЛЬСКОГО (АРХИПЕЛАГ СЕВЕРНАЯ ЗЕМЛЯ): ИССЛЕДОВАНИЯ 2019 Г

Morphological characteristics of three first-year ice ridges were investigated in the Shokalsky Strait in April and May 2019 by hot-water thermal drilling with the recording of penetration rate. Boreholes were drilled along the ice ridge cross-section with an interval of 0.25 m. The ice ridge cross-sectional profiles are presented. The sail height for the investigated ridges varied within 1.8-2.7 m, and the keel draft varied from 7.0 to 9.1 m. The ratio of the keel draft to the sail height was equal to 2.7-5.2, the thickness of the consolidated layer was 2.4-2.7 m. The mean porosity of the unconsolidated part of the keel in the ice ridges made up 28-36%. The porosity distributions for the unconsolidated part of the keel along the drilling profile are given for the analyzed ice ridges. The main feature of one of the ridges was an almost rectilinear slope of the keel, which laterally extended for 16 m.

The Average Shape of Sea Ice Ridge Keels

AbstractThrough analysis of over 64,000 ridge profiles identified from moored upward‐looking sonars, we identify a well‐defined average shape of pressure ridge keels that is concave or cusped, not triangular as widely assumed in other literature. On the basis of this average shape, we put forward a new, dimensional‐definition, of a pressure ridge cross‐section that follows a negative exponential form and allows an average pressure ridge cross section to be constructed with knowledge or choice of a single parameter. The horizonal asymptote of the profile represents the draft of the “background” ice in which the ridge is embedded. The draft of this background ice scales with keel depth and is typically greater than can be accounted through thermodynamic growth, indicating that ridges tend to be embedded in fields of mechanically thickened rubble. Using a variational ridge model we simulated keel shapes for a range of ridge building conditions. The model results agree well with the observations and indicate the cusped shape of an average ridge profile arises from the varying angle of horizontal shear in the ice cover when ridges form. The modeling results also explain the elongated tail of the area draft distribution of the pack.

Ultra-compact, broadband adiabatic passage optical couplers in thin-film lithium niobate on insulator waveguides.

We report the first demonstration of broadband adiabatic directional couplers in thin-film lithium niobate on insulator (LNOI) waveguides. A three LN-waveguide configuration with each waveguide having a ridge cross section of less than 1 square micron, built atop a layer of SiO2 based on a 500-µm-thick Si substrate, has been designed and constructed to optically emulate a three-state stimulated Raman adiabatic passage system, with which a unique counterintuitive adiabatic light transfer phenomenon in a high coupling efficiency of >97% (corresponding to a >15 dB splitting ratio) spanning telecom S, C, and L bands for both TE and TM polarization modes has been observed for a 2-mm long coupler length. An even broader operating bandwidth of >800 nm of the device can be found from the simulation fitting of the experimental data. The footprint of the realized LNOI adiabatic coupler has been reduced by >99% compared to its bulk counterparts. Such an ultra-compact, broadband LNOI adiabatic coupler can be further used to implement or integrate with various photonic elements, a potential building block for realizing large-scale integrated photonic (quantum) circuits in LN.

Nd:sapphire channel waveguide laser

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 σ- and π-polarization, respectively. A maximum slope efficiency with respect to incident pump power of 12% was achieved in σ-polarization with a ridge cross section of 40.8 × 2.6 µm2 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.

Microbeam high angular resolution x-ray diffraction in InGaN∕GaN selective-area-grown ridge structures

GaN-based 6-μm-wide ridge waveguides with InGaN∕GaN multiple-quantum-wells (MQWs) produced by metal organic vapor-phase epitaxy in the regime of selective-area growth have been studied with microbeam high angular resolution x-ray diffraction and reciprocal-space mapping. Variation of the strain from 0.9% to 1.05% and a factor of 3 for the thickness enhancement of the MQW period have been measured for different widths of the oxide mask surrounding the GaN-based ridges. Only when the trapezoidal shape of the ridge cross section is taken into account can the difference between the experimentally measured thickness enhancement and predictions of the long-range gas-phase diffusion model be reconciled.

An ultrasonic linear motor using ridge-mode traveling waves

A new type of ultrasonic linear motor is presented using traveling waves excited along a ridge atop a substrate. The ridge cross section was designed to permit only the fundamental mode to be excited during operation of the motor, with a Langevin transducer used as the source of vibration in this study. The ridge waveguide was first made of lossy media to avoid reflecting vibration energy back toward the vibration source, forming a traveling wave. A 5-mm-wide, 15-mm-tall rectangular acrylic ridge was used to move a slider placed upon it toward the vibration source, in opposition to the direction of the traveling wave transmitted along the waveguide ridge. Using a low-loss 3 x 6-mm aluminum rectangular ridge combined with a damper clamped onto the far end of the waveguide, similar results were obtained. To obtain bidirectional operation, the damper was replaced with a second Langevin transducer, giving a pair of transducers located perpendicularly to the ends of the ridge and driven with an appropriate phase difference. The moving direction of the slider was reversed by shifting this phase difference by about 180 degrees. With this simple configuration, it may soon be possible to fabricate a linear micromotor system on a silicon substrate or other semiconductor wafer adjacent to other electronic and optoelectronic devices.

Epitaxial Nd:YLF linear waveguide laser

We report laser operation in planar and linear Nd:YLF waveguide structures grown by liquid-phase epitaxy (LPE). We could reduce the relatively high threshold of 115-mW incident pump power observed for the planar waveguide to 8 mW in a ridge-type structure that we obtained by mechanical polishing and subsequent growth of a cladding layer. Substantial improvements seem possible with reduction of the losses caused by imperfect end-face reflection and scattering, as well as by use of techniques capable of producing smaller structures than the 40-microm-wide triangular ridge cross section that was obtained with polishing. Since the LPE technique is applicable to other activator ions as well, it might offer a route to development of low-threshold upconversion lasers.