Microcavity effects in an external-cavity surface-emitting laser

Microcavity-induced lasing threshold reduction and modulation of the spontaneous emission coherence length with cavity length in an external-cavity resonant-periodic-gain, surface-emitting laser is reported. In contrast to comparing different epitaxial growths, external-cavity operation allows changing the cavity length without affecting material properties as well as arbitrarily long resonator lengths. The transition to the macrocavity domain is observed by extending the cavity length beyond the spontaneous emission coherence length. The maximum change in the spontaneous emission rate induced by the cavity QED effect in the presence of resonant periodic gain is calculated. As expected, for cavities longer than several wavelengths, microcavity Fabry-Perot resonance effects dominate over cavity QED in determining the cavity-normal spontaneous emission power and coherence length. A simple model of the cavity-normal spontaneous emission coherence length and spontaneous emission power emitted from a Gaussian source placed in an ideal Fabry-Perot cavity is consistent with our observations     

采用平凸腔自准直输出的(Ce,Nd):YAG激光器

大多数小型手持式激光测距仪均采用平行平面谐振腔结构的Nd:YAG激光器作为测距光源,因其激光器的峰值功率不高,激光束散角差,重复工作频率低而使测距仪的性能受到一定限制。我们采用能同时压缩脉宽和束散角的平凸型非稳腔和热效率高的新型双掺(Ce,Nd):YAG晶体,装调出的激光器获得了18.6mJ能量,5ns脉宽,0.6mrad束散,峰值功率3.7MW的激光单脉冲输出。     

腔内光强增强型凹面光栅选支CO2 激光器研究

文中介绍了一种适用于腔内光化学反应的腔内光强增强型凹面光栅选支连续CO2激光器的设计及实验参数。由于光腔较长和增益较大，在00^01—10^00和00^01—02^00振转跃迁谱带分别有53条和49条谱线激光输出。得到00^01—10^00跃迁的最低增益线10p（56）输出功率2．5W，腔内功率约166．7W，腔内最大功率（10p（20）支线）为520．3W。     

Direct Measurement of Positronium HyperFine Structure: ～ A New Horizon of Precision Spectroscopy Using Gyrotrons ～

Positronium is an ideal system for research on QED, especially in a bound state. A discrepancy (3.9σ) is found recently between measured HFS values and the QED prediction (including up-to O(α ³ log α ^− 1), where α is the fine-structure constant.). It might be due to a contribution of unknown new physics or common systematic problems in all the previous measurements. A new method to measure HFS directly is performed using a high power gyrotron. The transition from ortho-positronium to para-positronium has been observed with 5 σ CL, which is the first observation of M1 transition in (sub)Terahertz region. New technologies of high power gyrotrons are developed for precision spectroscopy.     

Calculation of frequency and power characteristics of the composite metal-dielectric resonator using the method of partial regions

A new method for calculating the frequency and power characteristics of different modes of a microwave metal-dielectric resonator has been proposed. The results of measurements of experimental specimens are presented that are in good agreement with calculation results. The relationships of the frequency and power characteristics of a resonator as a function of its geometrical and electrophysical parameters were obtained by using the method of partial regions. A high sensitivity of the main mode resonant frequency to the thickness of air inhomogeneity was detected. In this case the introduction of inhomogeneity increases the resonator Q-factor. Thus, the proposed design can be used as a high-Q tunable resonator.     

基于新颖调谐谐振器的低相噪VCO设计

介绍了一种采用新颖谐振器的低相位噪声窄带压控振荡器(VCO)的设计方法。该谐振器采用源与负载横向交叉耦合结构,形成一个传输零点,提高了谐振器的Q值。该谐振器通过弱耦合与变容二极管连接,从而实现电压控制滤波器通带中心频率调谐。利用该谐振器设计了一个窄带VCO,并在先进设计系统(ADS)软件里仿真验证。该VCO中心频率6.15 GHz,在调谐电压从0到15 V的范围内调谐带宽60 MHz,相位噪声在整个调谐范围内优于-132 dBc/Hz@1MHz,输出功率为8.4 dBm,功率平坦度±0.1 dBm。     

Copper vapor laser unstable resonator oscillator and oscillator-amplifier characteristics

We have studied the properties of copper vapor lasers configured as oscillators with unstable resonator optics and as power amplifiers. With the unstable resonator, a 26-fold reduction in the oscillator beam divergence has been achieved over the value observed with stable optics without any power degradation. Time-dependent beam divergence effects in the unstable resonator have also been measured and explained. Small-signal gain, saturation fluence, and available stored energy density parameters have also been measured in oscillator amplifier experiments for both the 510.6 and 578.2 nm transitions as a function of the copper number density. These results quantify the maximum power per unit length available from these devices and furthermore, demonstrate efficient extraction of power from copper vapor lasers operated as amplifiers.     

Pump power stability range of single-mode solid-state lasers with rod thermal lensing

The pump power stability range of solid-state laser resonators operating in the TEM00mode has been thoroughly investigated. It has been shown that, for a very general resonator containing intracavity optical systems, rod thermal lensing engenders a pump power stability range which is a characteristic parameter of laser material and pump cavity, but is independent of resonator configuration. Stability ranges have been calculated and critically discussed for Nd:YAG, Nd:glasses, Nd: Cr: GSGG, and alexandrite. The independence of the pump power stability range from the resonator configuration has been experimentally demonstrated for a CW Nd:YAG laser.     

High-Q active resonators using amplifiers and their applications to low phase-noise free-running and voltage-controlled oscillators

This paper presents a new technique to design high-Q active resonators. The active resonators are then used in the design of low phase-noise oscillators. The proposed new technique uses an amplifier to generate a negative resistance, which compensates for the resonator losses and increases the Q factor. The active resonator using this technique shows a high loaded Q factor of 548.62 from measurement at the fixed 10-GHz resonant frequency. Considerations to design a voltage tunable active resonator is given and measurements show that the loaded Q factors exceed 500 with a 120-MHz tuning range. A low phase-noise free-running and voltage-controlled oscillator (VCO) were designed as an application of the proposed active resonators. The phase noise of the free-running oscillator using the active resonator is -114.36 dBc/Hz at 100-kHz offset, which is 14 dB lower than the phase noise of the passive resonator oscillator. In the case of a VCO using the active resonator, the phase-noise performance is below -110 dBc/Hz over the whole tuning range, which is lower 13 dB compared to the passive resonator VCO. The total dc power consumptions are approximately 500 mW.     

The Radiation of Electromagnetic Power by Microstrip Configurations

A new technique for calculating the radiation losses of microstrip configurations is presented. The method applies if the wavelength is large compared to the width of the conducting strip and the thickness of the dielectric wafer. It is shown that the radiated power, which is partly carried by "space waves" and partly by "surface waves," can be computed in terms of the specific inductance and the specific capacitance of the transmission line, without making any assumptions regarding the current distribution in the microstrip. It appears that the fraction of the radiated power carried by surface waves contains the frequency to a higher power than does the fraction carried by space waves and is therefore relatively small. The investigated configurations are the infinitely long transmission line excited by a voltage-slit, the half-wavelength straight resonator, the full-wavelength circular resonator, and the quarter-wavelength hair-pin resonator. It follows that the quality factor of the straight resonator and the circular resonator are inversely proportional to the square of the frequency, whereas the quality factor of the hairpin resonator is inversely proportional to the fourth power of the frequency.     

Direct imaging of a high-power diode laser cavity using a transparent indium-tin-oxide (ITO) contact

We describe a novel "see-through" indium-tin-oxide contact on the n-side of a high power unstable resonator semiconductor laser (URSL) that allows direct observation of the cavity during high power operation. Under optimized annealing conditions this transparent ITO contact has a low enough specific contact resistivity to permit normal high power CW operation of the URSL and allows the observation of filamentation. This contact scheme is applicable to a wide range of semiconductor lasers and is especially appropriate for high power devices. The same structure can also be used to obtain a 2-D thermal map of the laser cavity.     

环形腔YAG:Nd~(3 )激光器

在带有附加反馈镜的YAG:Nd~(3 )环形腔中,得到了定向比为30的单向输出。谱线宽度较之驻波腔压缩了十倍,输出功率并不降低。对其振荡时间特性提出了新的见解。     

内置透镜平平腔自调Q激光器的特性研究

文章在Cr4 + ∶Nd3 + ∶YAG自调Q激光器中,实验验证了内置透镜平平腔组成的等效腔具有比普通平凹腔更高的稳定性,并给出相应理论解释;实验中还观察到在泵浦功率增加时,输出功率、重复频率呈现极值特性和单脉冲能量增加近两倍等特殊实验现象。本文通过理论分析指出,引起基模光束半径和泵浦速率的动态变化主要影响因素是晶体内热透镜效应,且可通过调节腔长、内置透镜的位置等方式改变输出激光的重频、能量特性。这说明在自调Q激光器方面,内置透镜平平腔比普通平凹腔具有更大的设计灵活性。     

A wideband SAW resonator and its application to a VCO for mobileradio transceivers

A new wideband SAW resonator has been developed for SAW-VCOs used in mobile radio communication transceivers. The resonator is based on a repeated structure of pairs of electrically connected IDTs, which provides a high Q and a wide frequency bandwidth. An experimental SAW-VCO module measuring 8×8 mm² offers a frequency-variation bandwidth of about 20 MHz, a C/N of 75 dB, and an output power of 3-4 dBm at 900 MHz, satisfying the specifications for Japanese MCA and business-use radio transceivers     

缺陷地结构在微带均衡器设计中的应用

本文将缺陷地结构应用到微带功率均衡器的设计中。文中对比分析了加载缺陷地结构前后均衡器谐振枝节的特性以及缺陷地结构参数对谐振枝节性能的影响,在此基础上设计了缺陷地结构微带功率均衡器。加载缺陷地结构后可以得到更大的均衡量,同时也拓展了带宽,因而可以用较少的谐振枝节来实现更宽的均衡网络,保证了器件的小型化,为微带功率均衡器的设计提供了新的结构。     

光轴位置及腔镜变形对多折腔输出特性的影响

本文研究在高功率横流CO2激光器多折腔中,影响光轴位置的几个因素及对输出特性的影响,并用实验方法确定了多折腔的最佳光轴位置。研究了多折腔中反射镜产生形变的原因,并从谐振腔参数出发,找到了克服这类腔型反射镜形变对输出特性影响的措施。     

50-GHz passively mode-locked surface-emitting semiconductor laser with 100-mW average output power

We have developed a passively mode-locked optically-pumped vertical-external-cavity surface-emitting semiconductor laser (VECSEL) which delivers up to 100 mW of average output power at a repetition rate of 50 GHz in nearly transform-limited 3.3-ps pulses at a wavelength around 960 nm. The high-repetition-rate passive mode locking was achieved with a low-saturation-fluence semiconductor saturable absorber mirror (SESAM) incorporating a single layer of quantum-dots. The output power within a nearly diffraction-limited beam was maximized using a gain structure with a low thermal impedance soldered to a diamond heat spreader. In addition, we systematically optimized the laser resonator to accommodate for the strong thermal lens caused by the optical pumping. We measured the thermal lens dioptric power and present a numerical model which is in good agreement with the measurements and is useful for optimizing resonator designs. The experimental setup is very versatile and its design and construction are discussed in detail.     

高斯反射率方形平凹腔激光模场的有限元分析

利用柯林斯公式和边界有限元方法，将方形球面镜腔的衍射积分方程转化为矩阵方程，并对高斯反射率方形平凹腔的模场分布进行了数值计算。研究结果表明，高斯反射率方形平凹腔具有较好的选模性能，可以应用于高功率激光器以获得高质量的激光光束。     

Comparative Study of Quick Electron Detrapping and Random Telegraph Signal and Their Dependences on Random Discrete Dopant in Sub-40-nm NAND Flash Memory

In sub-40-nm Flash memory, random discrete dopant (RDD) effect modulates post program/erase (P/E) cycling $V_{t}$ instabilities through quick electron detrapping (QED) as well as random telegraph signal (RTS). In this letter, for the first time, we discuss the QED phenomenon and its physical origin by comparison with RTS phenomenon. P/E cycling stress not only aggravates the RTS but also generates the new phenomenon of QED which results from transiently trapped charges at near-interface defects during program. By applying a new test algorithm, we could successfully extract the QED component from RTS, both of which are modulated by RDD effect and worsen tail bits in multilevel-cell Flash memory.