Well-balanced ambipolar diketopyrrolopyrrole-based copolymers for OFETs,inverters and frequency doublers

Conjugated polymers with well-balanced ambipolar charge transport is essential for organic circuits at low cost and large area with simplified fabrication techniques.Aiming at this point,herein,a novel asymmetric thiophene/pyridine-flanked diketopyrrolopyrrole-based copolymer(PPyTDPP-2FBT)is designed and synthesized.Due to the effect of incorporating F atoms on molecular energy alignment and conjugation conformation,the PPyTDPP-2FBT copolymer exhibits typical V-shaped ambipolar field-effect transfer characteristics with well-balanced hole and electron mobilities of 0.64 and 0.46 cm^(2)V^(−1)s^(−1),respectively.Furthermore,organic digital and analog circuits such as inverters and frequency doublers are successfully constructed based on solution-processed films of the PPyTDPP-2FBT copolymers which show a typical circuit operating mode with a high gain of 133 due to the well-balanced electrical properties.In addition,PPyTDPP-2FBT-based devices also demonstrate good stability and batch repeatability,suggesting their great potential applications in organic integrated electronic circuits.

W-band high output power Schottky diode doublers with quartz substrate

W-band quartz based high output power fix-tuned doublers are analyzed and designed with planar Schot- tky diodes. Full-wave analysis is carried out to find diode embedding impedances with a lumped port to model the nonlinear junction. Passive networks of the circuit, such as the low pass filter, the E-plane waveguide to strip transitions, input and output matching networks, and passive diode parts are analyzed by using electromagnetic simulators, and the different parts are then combined and optimized together. The exported S-parameters of the doubler circuit are used for multiply efficiency analysis. The highest measured output power is 29.5 mW at 80 GHz and higher than 15 mW in 76-94 GHz. The highest measured efficiency is 11.5% at 92.5 GHz, and the typical value is 6.0% in 70-100 GHz.

A 5.4mW and 6.1% efficiency fixed-tuned 214GHz frequency doubler with Schottky barrier diodes

A Y-band frequency doubler is analyzed and designed with GaAs planar Schottky diode, which is flip-chip solded into a 50 μm thick quartz substrate. Diode embedding impedance is found by full- wave analysis with lumped port to model the nonlinear junction for impedance matching without the need of diode equivalent circuit model. All the matching circuit is designed ＂on-chip＂ and the mul- tiplier is self-biasing. To the doubler, a conversion efficiency of 6.1% and output power of 5.4mW are measured at 214GHz with input power of 88mW, and the typical measured efficiency is 4.5% in 200 - 225 GHz.

The ultimate strength of doubler plate reinforced Y-joints under compression loading

It is common practice in the offshore industry to solve the punching shear problem due to compression by using doubler plate. The finite-element method is a useful tool for studying this problem. The aim of this paper is to study the static strength of doubler plate reinforced Y-joints subjected to compression loading. The finite-element method is adopted in numerical parametric studies. The individual influences of the geometric parameters βand τd （doubler plate to chord wall thickness ratio） and ld/d1（dubler plate length to brace diameter ratio） on the ultimate strength are made clear. The results show the size of plate may have important effects on the strength of reinforced joints. It is found that the ultimate strength of Y-joints reinforced with appropriately proportioned doubler plates can be greatly improved nearly up tothree times to un-reinforced Y-joints.

An E-band CMOS frequency quadrupler with 1.7-dBm output power and 45-dB fundamental suppression

This paper presents an E-band frequency quadrupler in 40-nm CMOS technology.The circuit employs two push-push frequency doublers and two single-stage neutralized amplifiers.The pseudo-differential class-B biased cascode topo-logy is adopted for the frequency doubler,which improves the reverse isolation and the conversion gain.Neutralization tech-nique is applied to increase the stability and the power gain of the amplifiers simultaneously.The stacked transformers are used for single-ended-to-differential transformation as well as output bandpass filtering.The output bandpass filter enhances the 4th-harmonic output power,while rejecting the undesired harmonics,especially the 2nd harmonic.The core chip is 0.23 mm^(2)in size and consumes 34 mW.The measured 4th harmonic achieves a maximum output power of 1.7 dBm with a peak conversion gain of 3.4 dB at 76 GHz.The fundamental and 2nd-harmonic suppressions of over 45 and 20 dB are achieved for the spectrum from 74 to 82 GHz,respectively.

High frequency doubling efficiency THz GaAs Schottky barrier diode based on inverted trapezoidal epitaxial cross-section structure

A high-performance terahertz Schottky barrier diode(SBD)with an inverted trapezoidal epitaxial cross-sectional structure featuring high varactor characteristics and reverse breakdown characteristics is reported in this paper.Inductively coupled plasma dry etching and dissolution wet etching are used to define the profile of the epitaxial layer,by which the voltage-dependent variation trend of the thickness of the metal-semiconductor contact depletion layer is modified.The simulation of the inverted trapezoidal epitaxial cross-section SBD is also conducted to explain the physical mechanism of the electric field and space charge region area.Compared with the normal structure,the grading coefficient M increases from 0.47 to 0.52,and the capacitance modulation ratio(C^(max)/C_(min))increases from 6.70 to 7.61.The inverted trapezoidal epitaxial cross-section structure is a promising approach to improve the variable-capacity ratio by eliminating the accumulation of charge at the Schottky electrode edge.A 190 GHz frequency doubler based on the inverted trapezoidal epitaxial cross-section SBD also shows a doubling efficiency of 35%compared to that 30%of a normal SBD.

Generation of self-oscillations from a singly resonant periodically poled potassium titanyl phosphate crystal frequency doubler

We report on the generation of self-oscillations from a continuously pumped singly resonant frequency doubler based on a periodically poled potassium titanyl phosphate crystal （PPKTP）. The sustained square-wave and staircase curve of self-oscillations are obtained when the incident pump powers are below and above the threshold of subharmonic-pumped parametric oscillation （SPO）, respectively. The self-oscillations can be explained by the competition between the phase shifts induced by cascading nonlinearity and thermal effect, and the influence of fundamental nonlinear phase shift by the generation of SPO. The simulation results are in good agreement with the experiment data.

A GaAs planar Schottky varactor diode for left-handed nonlinear transmission line applications

The left-handed nonlinear transmission line （LH-NLTL） based on monolithic microwave integrated circuit （MMIC） technology possesses significant advantages such as wide frequency band, high operating frequency, high conversion efficiency, and applications in millimeter and submillimeter wave frequency multiplier. The planar Schottky varactor diode （PSVD） is a major limitation to the performance of the LH-NLTL frequency multiplier as a nonlinear component. The design and the fabrication of the diode for such an application are presented. An accurate large-signal model of the diode is proposed. A 16 GHz-39,6 GHz LH NLTL frequency doubler using our large-signal model is reported for the first time. The measured maximum output powers of the 2nd harmonic are up to 8 dBm at 26.4 GHz, and above 0 dBm from 16 GHz to 39.6 GHz when the input power is 20 dBm. The application of the LH-NLTL frequency doubler furthermore validates the accuracy of the large-signal model of the PSVD.

Simulation of multiphase boost DC-DC converter with the stable control strategy

The multiphase boost DC-DC converter with stable control strategy is presented. Multi- phase boost DC-DC converter is designed for high voltage and high power applications, and could be achieved by the adjustment of voltage doubler rectifiers on the secondary side of high frequency transformers. The stable control strategy for three phase boost DC-DC converter has been utilized during simulation in this study and this strategy can be extend to N-number of phases. The stable control strategy consists of only three voltage loops, which are sufficient for appropriate and efficient operation of three phase boost DC-DC converter. With the stable control strategy, the equal power balance sharing can be obtained between input and output. The stability of control strategy has been evaluated by simulating the multiphase boost DC-DC converter for the same and mismatch turn ratios of high frequency transformers. The simulation result is good and the objective of the strategy is a- chieved.

All-solid-state narrow-linewidth 455-nm blue laser based on Ti:sapphire crystal

A compact, all-solid-state, narrow-linewidth, pulsed 455-nm blue laser based on Ti：sapphire crystal is developed. Pumped by a 10-Hz, frequency-doubled all-solid-state Nd：YAG laser and injection-seeded by an external cavity laser diode, the narrow-linewidth 910-nm laser with pulse width of 20 ns is obtained from a Ti：sapphire laser. 3.43-mJ blue laser can be obtained from the laser system by frequency-doubling with BBO crystal. This research is very useful to determine the roadmap of developing the practical, high power blue laser. This kind of laser will have potential application for underwater communication.

Efficient stable simultaneous CW dual-wavelength diode-end-pumped Nd:YAG laser operating at 1.319 and 1.338 μm

An efficient, stable diode-end-pumped simultaneous continuous-wave （CW） dual-wavelength laser operating at 1.319 and 1.338 ttm in a Nd：YAG crystal has been demonstrated. A total output power of 6.3 W is achieved at an absorbed pump power of 15 W, with a slope efficiency of 43.5%. The instability of output power is less than 1%. With a type II critical phase-matched KTP crystal inserted into the cavity as frequency doubler, a maximum output power of 200 mW in red region is acquired. In addition, a sixwavelength laser operation at 1.319 μm, 1.338 μm, 1.356 μm, 659.5 nm, 669 nm, and 678 nm is observed.

Continuous-wave green laser of 34 W by intracavity frequency doubling in diode-side-pumped Nd:YAG/KTP

Continuous-wave green laser with a maximum power of 34 W has been obtained by intracavity frequency doubling with KTP in diode-side-pumped Nd：YAG. The Nd：YAG/KTP green laser has a simple three- mirror V-fold cavity structure. The optical-to-optical conversion efficiency is 9.5%. The instability of the laser is measured when the output powers are near 16, 21, 30, and 34 W after the beam is filtered. At the maximum output power, the M^2 factor is measured to be 8.

Frequency-stabilized semimonolithic frequency doubler with high output power

We present a semimonolithic frequency-doubler from 1080 to 540 nm with 80% doubling efficiency and up to 849-mW output power of green light. A frequency-stabilized laser diode (LD) pumped continuous wave (CW) Nd:YAP laser is used as the pump source of the doubler consisting of an α-cut KTP crystal and an input mirror. The frequency stabilities of the output second harmonic wave are better than ±246 kHz and ±2.3 MHz in 1 and 30 minutes, respectively, and the intensity fluctuation is less than ±0.65%.

Frequency doubling of narrow-linewidth pulsed fiber laser

A pulsed master oscillator power amplifier system is constructed using a double-cladding polarized Yb- doped fiber and an all-fiber Q-switched narrow-linewidth pulsed laser used as seed laser. This system has a high repetition rate and provides a nanosecond pulsed laser with a narrow linewidth and linear polarization. Moreover, it generates amplified radiation with up to 14 W of average power, narrow linewidth （full-width at half-maximum is smaller than 0.12 am）, linear polarization at 1080-am wavelength, repetition rate of 51 kHz, and pulse duration of approximately 50 ns. Based on this pulsed amplified radiation, 3.5 W of green laser, with an optical-to-optical efficiency of 27.3%, is obtained via single-pass frequency doubling using a noncritical phase matching KTP crystal.

Low-power-pumped high-efficiency frequency doubling at 397.5 nm in a ring cavity

We report low pump power high-efficiency frequency doubling of a fundamental laser beam at 795 nm, corresponding to the rubidium D1 line, to generate UV light at 397.5 nm using a periodically poled KTi OPO4（PPKTP） crystal in a ring cavity. We obtain maximum stable output power of 49 m W for mode-matching pump power of 110 m W, corresponding to 45% raw efficiency（56% net efficiency when considering the output coupling mirror’s 80% transmission）. This is the highest efficiency obtained at this wavelength in PPKTP with such low pump power. We obtain 80% beam coupling efficiency to single-mode fiber, demonstrating high beam quality.

High contrast amplification at 1053 nm limited by pulse stretching-compressing process

We report on our high-contrast laser based on high-contrast, high-energy seed injection, low-gain optical para- metric chirped pulse amplification （OPCPA）, and Nd：glass amplifiers, which can be used as the high-contrast front end of a high-power Nd：glass chirped pulse amplification （CPA） laser system. The energy of the stretched 1053 nm high-contrast seed pulse increases to 60 DJ by optimizing the frequency doubling crystal in the pulse cleaning device. After passing through a two-stage low-gain OPCPA, a 2-pass 2-rod Nd：glass amplifier, and a compressor the amplified pulse of 131 mJ/282 fs is achieved. The third-order correlation scanning measurement shows that the pulse contrast in the tens of ps range is about 10^-7-10^-8. With the high-contrast seed passing through the stretcher and compressor only, the contrast measurement indicates that the stretching-compressing process leads mainly to the contrast degradation of the amplified pulse.

Simulation study on an improved frequency-doubled triangular-shaped pulse train generator with reduced harmonic distortion

An approach to reducing the harmonic distortion in frequency-doubled triangular-shaped pulse train generation is proposed. It requires a dual-parallel Mach Zehnder modulator followed by a section of dispersive fiber, as the key component. The basic principle is to make the expression of optical intensity approximately equal to the Fourier expansion of idea triangular-shaped waveform. A detailed expression of the final optical intensity is given by theory and then verified by simulation. It is found that the impact of the undesired harmonic distortion is greatlv reduced.

Increased temperature acceptance bandwidth in frequency-doubling process using two different crystals

The temperature acceptance bandwidth of second-harmonic generation（SHG） can be dramatically improved by using two different kinds of nonlinear crystals with opposite signs of temperature derivation of phase mismatch. We study two SHG processes for the existing 1064 and 1550 nm high-average-power lasers. The numerical results show that the temperature acceptance bandwidth for SHG at 1064 nm can be three to five times larger than that of traditional single-crystal design, and it is also larger than that of using temperature-insensitive yttrium calcium oxyborate crystal. Importantly, the proposed design is applicable to various wavelengths, which suggests its potential in high-average-power SHG applications.

High power red laser generation by second harmonic generation with GTR-KTP crystal

In this Letter, a gray-tracking-resistant--potassium titanyl phosphate （GTR-KTP） crystal is used for intracav- ity frequency doubling red laser generation for the first time. Under the 808 nm LD pump power of 180 W, as high as 12.5 W of red laser output is obtained with the optimum repetition rate of 7 kHz. Within the red laser power variation range between the maximum to 70%, a temperature tolerance is measured to be 35℃. The results prove that GTR-KTP should be a potential nonlinear crystal for red laser generation.

Precise calculation of the KTP crystal used as both an intracavity electro-optic Q-switch and a second harmonic generator

A method of precisely calculating the external applied voltage and the optimum type-Ⅱ phase matching angles for KTP crystal, which is used as both an intracavity electro-optic （EO） Q-switch and a frequency doubler, is presented. The effective EO coefficient along the phase-matching direction is defined to calculate the half-wave voltage and the quarter-wave voltage, and the precise calculation for the phase matching angles in the condition of KTP crystal optimum second harmonic phase matching is theoretically realized.