Transverse energy confinement and resonance suppression in SAW resonators using low-cut lithium tantalate

This paper discusses the applicability of double busbar design to surface acoustic wave (SAW) devices employing low-cut lithium tantalate (LT) with multi-layered structure. This design offers good energy confinement, scattering loss suppression and transverse mode suppression for a wide frequency range. In addition, the effectiveness of manipulating the slowness curve shape for transverse mode suppression is demonstrated. First, three different lateral edge designs are applied to the layered SAW configuration on low-cut LT, and their performances are compared using the periodic 3-dimensional finite-element method powered by the hierarchical cascading technique. Then, the discussion is extended to influence of the SAW slowness shape to the transverse mode suppression.

Особенности одночастотной генерации в квантово-каскадных лазерах спектрального диапазона 7.5-8.0 μm с малой длиной резонатора

The possibility of realizing single-mode emission in quantum-cascade lasers due to modulation of output optical losses in a Fabry-Perot cavity is demonstrated. For the active region of the 7.5–8.0 μm spectral range, two-phonon resonance design we used thus the 50 stages and waveguide layers based on indium phosphide made it possible to realize single-mode lasing at 7.765 μm and at temperature of 292 K. Side-mode suppression ratio was about 24 dB and remained the same with an increase in the current pumping up to 1.2 of the threshold current values. The coefficient of wavelength shift with temperature (temperature tuning) in the single-mode lasing regime was 0.56 nm / K.

High-power single-mode 894 nm VCSELs operating at high temperature (> 2 mW @ 365 K)

In this study, we realize the high-power output of a single-mode 894 nm vertical-cavity surface-emitting laser (VCSEL) at high temperature. The effects of the dimensional parameters of oxide aperture and surface relief on the transverse mode and threshold gain of VCSEL were analyzed. Through collaborative optimization of the oxide aperture and relief, the VCSEL with 8 µm oxide aperture diameter and 5 µm surface relief inner diameter can operate at high temperature of 365 K with single-mode output power of 2.02 mW and side-mode suppression of 29.2 dB.

Dynamic characteristics and noise modelling of directly modulated quantum well-dots microdisk lasers on silicon

The small-signal amplitude modulation, threshold, and spectral characteristics of microdisk lasers with InGaAs/GaAs quantum well-dots active region were studied jointly with the spectral and threshold parameters of edge-emitting lasers made from the same epitaxial heterostructure. Using the obtained material parameters, the relative intensity noise of the microdisk lasers was calculated as a function of the bias current and side-mode suppression ratio. It is shown that the integral noise is low enough for error-free optical data transmission with the maximum possible bitrate limited by the microdisk modulation bandwidth, if the bias current is above 1.7× threshold current (for side mode suppression ratio > 20 dB).

Flat OFC Generation Based on DPMZM Cascaded Dual-Parallel PolM with Frequency Multiplication Circuit

An innovative scheme to generate the high-quality OFC based on DPMZM cascaded dual-parallel PolM with frequency multiplication circuit is proposed and demonstrated. In the scheme, 5 comb lines are generated in the first-stage generator, and the comb line is expanded to 11 times in the second-stage generator. The theoretical model of the overall scheme is established and analyzed. In this scheme, 66-line OFC is generated and the flatness is 0.73 dB, the side mode suppression ratio (SMSR) is 14.19 dB, and the optical signal noise ratio (OSNR) is about 29 dB.

Influence of displacement and patterning of phase shifters for piston mode operation of temperature compensated surface acoustic wave resonators on SiO2/LiNbO3 structure

This paper discusses influence of displacement and patterning of phase shifters for piston mode operation of the temperature compensated (TC) surface acoustic wave (SAW) resonator on SiO2/LiNbO3 structure. As the phase shifters, Cu metals placed on the top surface of SiO2 are considered. First, the conventional Cu stripes are chosen, and their displacement are considered from IDT aperture edges. It is shown that achievable transverse mode suppression is almost identical when the stripe shape is adjusted for each case. Next, Cu dots are considered as patterned phase shifters. It is shown comparable transverse mode suppression is possible also for this case. However, relatively strong SAW lateral leakage occurs when they are placed above IDT fingers. These results indicate that location and pattern can be added as design parameters for the phase shifters on SiO2. It is favorable for further enhancement of total device performances.

Tunable single-mode chip-scale mid-infrared laser

Portable mid-infrared (mid-IR) spectroscopy and sensing applications require widely tunable, chip-scale, single-mode sources without sacrificing significant output power. However, no such lasers have been demonstrated beyond 3 μm due to the challenge of building tunable, high quality-factor (Q) on-chip cavities. Here we demonstrate a tunable, single-mode mid-IR laser at 3.4 μm using a tunable high-Q silicon microring cavity and a multi-mode Interband Cascade Laser. We achieve single-frequency lasing with 0.4 mW output power via self-injection locking and a wide tuning range of 54 nm with 3 dB output power variation. We further estimate an upper-bound effective linewidth of 9.1 MHz and a side mode suppression ratio of 25 dB from the locked laser using a scanning Fabry-Perot interferometer. Our laser platform based on a tunable high-Q microresonator can be expanded to higher wavelength quantum-cascade lasers and lead to the development of compact, high-performance mid-IR sensors for spectroscopic applications.