Coupled Output Power Research Articles

Integration of O-band quantum dot lasers with AlGaN/GaN waveguides.

We integrate edge-emitting etched-facet InAs/GaAs quantum dot (QD) lasers to an AlGaN/GaN-on-sapphire waveguide platform via micro-transfer printing. The lasers are placed into a trench etched into the sapphire substrate so as to transversely align the waveguides. The AlGaN/GaN waveguide structure is designed to allow for tolerant alignment of the active lasing mode to the passive waveguide mode. 4 μm wide waveguides show a TE propagation loss of 4.5 dB/cm. For a QD laser with a 1.2 mm long cavity and 3.5 μm wide ridge waveguide, 2.3 mW was measured at 80 mA under continuous wave conditions from the end of a 0.64 cm long 4 μm wide waveguide with an estimated coupling efficiency of >20 %. The measured coupled output power is 1.5 mW at 70°C and 100 mA. To our knowledge, this is the first demonstration of the heterogeneous integration of a GaAs lasing device to a GaN-based PIC by any means. The results show real promise for GaN to be a suitable platform for integrated photonics applications requiring O-band operation.

Adaptive Frequency Droop Feedback Control-Based Power Tracking Operation of a DFIG for Temporary Frequency Regulation

Frequency regulation scheme of doubly-fed induction generators (DFIGs) are implemented to improve the frequency stability achieving by rotor speed control. However, the coupling dynamics between the maximum power point tracking operation control loop and frequency regulation control loop would impair the frequency regulation capability. To eliminate the adverse influences, firstly, analytical derivation for coupling output power dynamics is represented when adopting frequency regulation scheme of the DFIG. Then, an adaptive frequency droop feedback control based on power tracking operation strategy, which is a decoupling control scheme for frequency regulation, is proposed to respond the dynamic grid frequency without reserving power. The frequency deviation-based droop control with dynamics gains is used to calculate the coefficient of power tracking operation of the DFIG. The system stability with various power tracking operation of the DFIG is analyzed, in addition, the stable boundary is used to limit the setting of coefficient of power tracking operation. Simulations are carried based on an EMTP-RV simulator. It is found that the suggested adaptive frequency droop feedback control based on power tracking strategy can provide dual frequency regulation capability and reduce the maximum frequency excursion under various scenarios.

Solving the spectral gap problem with a four-mirror bow-tie cavity in waveguide free-electron laser oscillators

The generation of intense coherent radiation pulses in the far-infrared and terahertz regimes is of considerable interest to the free-electron laser (FEL) radiation user community. At long wavelengths, the diffraction effect can be quite severe, therefore, an optical waveguide is required to confine the radiation field. However, it will also bring about some new phenomena, and the most noteworthy one is the spectral gap phenomenon: at some particular wavelengths, regardless of electron beam adjustments, the coupling efficiency and output power of waveguide FEL oscillators drop significantly. Such spectral gap has an adverse effect on experimental results since numerous experiments require continuous spectral scanning. In this paper, we propose to utilize a bow-tie cavity instead of conventional cavities to the waveguide FEL to solve the spectral gap problem. The simulation was carried out based on the parameters of FELiChEM, a newly built user facility in China. Numerical simulation code OPC combining with modified GENESIS is used to enable the modelling, for the first time, of a bow-tie cavity based FEL in the far-infrared wavelength regime. The simulation results indicate that this novel structure can effectively eliminate the spectral gaps and substantially enhance long-wavelength laser performance.

Multi-octave mid-infrared supercontinuum generation in tapered chalcogenide-glass rods.

We report on the experimental development of short-tapered chalcogenide-glass rods for mid-infrared supercontinuum generation. Multi-octave spectral broadening of femtosecond laser pulses is demonstrated from 1.6 to 15.6 µm in a 5-cm-long tapered Ge20Se70Te10 rod with a waist diameter of 25 µm. Despite the multimode nature of the optical waveguide used, this work clearly shows the potential of such simple post-processed rods for advancing fiber SC sources with infrared glasses, thereby unlocking new possibilities in terms of coupling efficiency, spectral coverage, and output power.

Coupling coefficient calculation and optimization of positive rectangular series coils in wireless power transfer systems

In wireless power transfer (WPT) systems using magnetic coupling resonance, when there is a registration deviation between the transmitting and receiving coils, there will be significant fluctuations in the coupling coefficient, output power, and transmission efficiency, which will seriously affect the stability of the WPT system. The coupling coefficient is related to the length and width of the rectangular coil, number of turns, mutual geometric position, and space magnetic medium, making it difficult to maintain a constant value when the coil is offset. A single-emitter two-receiver positive-series rectangular coils structure and a method of calculating the structure are proposed. Then an optimization method for mutual inductance was proposed, and the structural parameters that met the design requirements were obtained using the proposed optimization method. The calculation formula for coupling coefficient was verified through simulation and experiments. The results showed that when the offset distance of the receiving coil along the Y-axis (driving direction) and X-axis reaches half of the length of the transmitting coil and 10 cm, the coupling coefficient, transmission efficiency, and output power remain almost unchanged.

Over-67-GHz-Bandwidth Membrane InGaAlAs Electro-Absorption Modulator Integrated With DFB Laser on Si Platform

We fabricate a membrane InGaAlAs electro-absorption modulator (EAM) integrated with a distributed feedback (DFB) laser combining direct wafer bonding and epitaxial regrowth of InP-based layers on a silicon-on-insulator wafer. Heterogeneous integration of an InP-based multiple-quantum-well (MQW) layer into the Si photonics simplifies the integration of the O-band EAMs and laser diodes (LDs). EAMs and LDs can be fabricated using the same MQW layer because of the wide operating range and the direct bandgap of the MQWs. A compact and high-speed lumped-electrode EAM can be made because the membrane lateral p-i-n diode structure has low capacitance and a large optical confinement factor. The effective-refractive-index matching between the membrane InP and Si layers enables the DFB laser to be fabricated with a low-loss supermode waveguide whose MQW core was optically coupled to the Si core. The fabricated 100-μm-long membrane EAM has a high modulation efficiency of about 3 dB/V at 1260 nm and E-O bandwidth of over 67 GHz even without a 50-ohm termination. The EAM-integrated DFB laser has a fiber coupled output power of about −2 dBm and clear eye openings with an extinction ratio of 3.8 and 3.2 dB for 100- and 112-Gbit/s non-return-to-zero signals, respectively.

Size-dependent and nonlinear magneto-mechanical coupling characteristics analysis for extensional vibration of composite multiferroic piezoelectric semiconductor nanoharvester with surface effect

We study the extensional vibration of composite multiferroic piezoelectric semiconductor (PS) nanoharvester driven via a time-harmonic magnetic field. A theoretical analysis about working performances of device is performed based on zero-order plate equations with surface and nonlocal effects, consisting of a nonlinear magneto-mechanical coupling constitutive model for giant magnetostrictive material Terfenol-D and a linear phenomenological theory of PS material ZnO. Numerical results indicate that the basic bahaviors (including resonant frequency, bandwidth characteristic, magneto-electric (ME) coupling effect, output power and energy conversion efficiency) of the nanoharvester, can be dramatically improved through circuit types, semiconduction, external magnetic field, pre-stress and surface effect. This work is essential and crucial for understanding the size-dependent and nonlinear mechanical behaviors of multiferroic PS nanodevices under the extremely complex magnetic field and pre-stress field environments.

Interleaved Capacitive Coupler for Wireless Power Transfer

Capacitive power transfer is becoming an attractive alternate for wireless chargers. A coupler with large self- and mutual capacitance is desirable from the power and efficiency perspective. However, state-of-the-art couplers suffer from the tradeoff design issue between these two types of capacitance. In order to improve the required capacitance, an interleaved capacitive coupler is proposed and evaluated based on the Maxwell-based simulation. Using more plates, it can effectively use the coupling space to maintain the required self- and mutual capacitance, while minimize the cross coupling effects. Meanwhile, the new coupler is also helpful to reduce the radioactive electric field, and the high-radiation region is reduced dramatically. In the experiment, three types of couplers are built with the same coupling space, compensations, and output power. The proposed interleaved structure can achieve the highest efficiency and minimum radiation.

A 183-GHz FMCW Transceiver Module for Wireless Fuse Applications

This paper presents the design, construction, and testing of a 183-GHz FMCW transceiver module for wireless fuse applications. The transmitter consists of a square-triangle wave converter, a Ku-band VCO, a 91.5-GHz × 2 × 3 multiplying and amplifying chain, a 10-dB multi-hole directional coupler, and a 183-GHz frequency doubler. For the multiplying chain, the generated 91.5-GHz signal power is partly coupled out by the 10-dB coupler. The coupled output power is used as local oscillator (LO) signal to pump the 183-GHz subharmonic mixer (SHM). The receiver is cascaded by a 183-GHz SHM and a low-noise immediate frequency (IF) amplifier. The measured typical output power of the 183-GHz transceiver is 48 mW and the minimum noise temperature of the receiver is 620 K at 181 GHz. At 5-mm and 10-mm detection distance, the measured signal noise ratio (SNR) of transceiver IF signal is higher than 30 dB and 17 dB at 10 KHz bandwidth, respectively. The SNR is high enough for the following signal processing.

Hybrid integrated InP-Si3N4 diode laser with a 40-Hz intrinsic linewidth.

We demonstrate a hybrid integrated and widely tunable diode laser with an intrinsic linewidth as narrow as 40 Hz, achieved with a single roundtrip through a low-loss feedback circuit that extends the cavity length to 0.5 meter on a chip. Employing solely dielectrics for single-roundtrip, single-mode resolved feedback filtering enables linewidth narrowing with increasing laser power, without limitations through nonlinear loss. We achieve single-frequency oscillation with up to 23 mW fiber coupled output power, 70-nm wide spectral coverage in the 1.55 μm wavelength range with 3 mW output and obtain more than 60 dB side mode suppression. Such properties and options for further linewidth narrowing render the approach of high interest for direct integration in photonic circuits serving microwave photonics, coherent communications, sensing and metrology with highest resolution.

Membrane III-V/Si DFB Laser Using Uniform Grating and Width-Modulated Si Waveguide

Membrane buried-heterostructure III-V/Si distributed feedback (DFB) lasers with a stopband-modulated cavity on a Si substrate have been developed. The membrane III-V layers with 230-nm thickness enable us to construct an optical supermode with a 220-nm-thick Si waveguide that is used in standard Si photonics platform. We employ a uniform grating and Si waveguide, in which Si waveguide width is modulated to control the center wavelength of the stopband. The cavity can be designed by controlling the modulation width and modulation length of Si waveguide. Therefore, it is easy to engineer and fabricate the laser cavity compared with the cavity using λ/4-phase shift grating. Output light from the cavity is coupled to Si waveguide through InP inverse taper waveguide, and then coupled to SiOx waveguide through Si inverse taper waveguide, which provides the 2-dB fiber coupling loss. We have demonstrated single-mode lasing by using Si waveguide, where its width is increased 80 nm at the center of the cavity. The threshold current and maximum fiber output power are 3 mA and 4 mW, respectively. By extending the active region length to 1 mm, 17-mW fiber coupled output power is obtained. High-temperature operation up to 130 °C is also obtained with a 1-mW fiber output power.

Integrated Control Strategy for Inductive Power Transfer Systems with Primary-Side LCC Network for Load-Average Efficiency Improvement

An inductive power transfer (IPT) system has lower peak efficiency and significantly lower load-average efficiency over the entire range of output power than typical power conversion systems because it transmits power wirelessly through magnetically coupled coils. In order to improve the load-average efficiency of the IPT system, this paper proposes an integrated control strategy consisting of full-bridge, phase-shift, and half-bridge control modes. The coupling coefficient and output power conditions for each control mode are theoretically analyzed, and the proposed control algorithm is established. In order to verify the analysis results, a 3.3 kW IPT system prototype is constructed, and it is experimentally verified that the load-average efficiency is improved by up to 3.75% with respect to the output power when using the proposed control scheme. In addition, the proposed control has the additional advantage that it can be directly applied to the existing IPT system without changing or adding hardware.

III-V-on-silicon anti-colliding pulse-type mode-locked laser.

An anti-colliding pulse-type III-V-on-silicon passively mode-locked laser is presented for the first time based on a III-V-on-silicon distributed Bragg reflector as outcoupling mirror implemented partially underneath the III-V saturable absorber. Passive mode-locking at 4.83GHz repetition rate generating 3ps pulses is demonstrated. The generated fundamental RF tone shows a 1.7kHz 3dB linewidth. Over 9mW waveguide coupled output power is demonstrated.

Tapered fused fiber bundle coupler capable of 1 kW laser combining and 300 W laser splitting

A high efficiency 7 × 1 multimode fiber coupler using the method of fusion and tapering is reported. This coupler can be applied to combine laser power, ad it can be used as a 1 × 7 splitter with reversible simultaneously. In the experiment, for combiner, coupling output power of 1032 W is obtained with the input power of 1066 W. The total coupling efficiency is 96.8%. The average insertion loss of each input fiber is 0.14 dB at ∼150 W input power. To splitter, the sum of 7 output ports power is 294 W with the input power of 341 W, and the insertion loss is about 13.8%. This fiber coupler can be applied in pumping all-fiber double clad fiber laser, as well as power combination and splitting of fiber lasers.

Research on Output Power of Plasma for PCVD Synthesizing Silica Glass

Super purity silica glass was synthesized by Plasma Chemical Vapor Deposition (PCVD) method, during which inductively coupled plasma was used as the heat source. Influence of structure factor of tube and working gas on output power were discussed. The structure factor of tube was confirmed by analyzing the relation between structure factor of tube and coupling efficiency. With the increase of coupling efficiency, output power and plasma radius grow bigger. Super purity silica glass can be successfully synthesized when air was used working gas, during which input power was 100kW and output power reached to 40kW.

Highly efficient and high output power of erbium doped fiber laser in a linear cavity configuration

A simple Erbium Doped Fiber Laser (EDFL) in linear cavity configuration is reported. The cavity design is based on an FBG as a back reflector, and a loop back optical circulator with an output coupler as the front reflector. Different coupling ratios of the coupler are tested and 50: 50 provides the highest coupling output power of 22.06 dBm (160.7 mW). The pump power conversion efficiency is about 95% when pumping with two pump lasers at 1460 and 1490 nm with combined pumping power of 545 mW. The laser output has a measured linewidth of 0.0179 nm.

Vertical coupling between gap plasmon waveguides

This work examines vertical coupling between gap plasmon waveguides for use in high confinement power transfer and power splitting applications at 1.55 microm free space wavelength. The supermode interference method is used to obtain key coupler performance parameters such as coupling length, extinction ratio, net coupled output power, radiated power, and reflected power as a function of waveguide center-to-center spacing, core refractive index, and gap width. The initial power distribution among the two coupler supermodes is obtained via the mode matching method for a single input waveguide feed. Excellent agreement with three-dimensional finite difference time domain simulations is observed for the case of square 50 nm gaps with core refractive indices of 2.50 and a center-to-center spacing of 112 nm. Local maxima in the net coupled output power are found to coincide with local minima in the coupling length. An increase in the core refractive index from 1.00 to 2.5 increases the local maximum net coupled output power from 6.4% to 49% but decreases the extinction ratio from 12.7 to 6.94. A sweep of the width of the core from 25 to 100 nm increases the net coupled output power from 43.7% to 52.0%, but increases the coupling length from 1.58 to 3.19 ???m and decreases the extinction ratio from 7.39 to 6.57.

Nonlinear Effects Analysis in DBR Lasers: Applications to DBR-SOA and New Double Bragg DBR

This paper presents a theoretical and experimental study of nonlinear effects in distributed Bragg reflector (DBR)-type tunable lasers, which are responsible for asymmetric spectral or power characteristics, and for hysteresis phenomena. We propose an optimized DBR semiconductor optical amplifier design that suppresses these effects, making the control simpler and more reliable, while maintaining the same performances as a DBR (16 nm tuning, 40 dB side mode suppression ratio, 20 mW coupled output power). Aiming to reach C-band tuning range with only one Bragg current control and reduced nonlinear effects, a new double Bragg DBR laser is proposed.

A compact external cavity wavelength tunable laser without an intracavity etalon

We propose a novel external cavity wavelength tunable laser (ECTL) configuration without an etalon inside the cavity. ECTL consists only of a semiconductor optical amplifier with an integrated phase section, and a liquid crystal tunable mirror. We successfully demonstrated excellent performances of the ECTL with fiber coupled output power of more than 50 mW over a 40-nm tuning range, sidemode suppression ratio of better than 45 dB, relative intensity noise of better than -148 dB/Hz, and linewidth of narrower than 2.3 MHz

1 W fibre coupled power InGaAsP/InP 14xx pump laser for Raman amplification

A 1 W record singlemode fibre coupled output power using 1460 nm InGaAsP/InP non-tapered buried ridge lasers has been demonstrated. The impact of the bandgap of the passive quaternary waveguide on internal loss was investigated. Optimised design allows internal losses as low as 3.3 cm−1, external efficiency of 0.46 W/A for a 3 mm-long laser and symmetrical (12°×12°) far-field pattern.