Solid-state Amplifier Research Articles

The Transistor, an Emerging Invention: Bell Labs as a Systems Integrator Rather Than a ‘House of Magic’

The transistor is one of the most consequential human inventions with dissemination of the eventual MOS-FET design estimated to exceed one quintillion devices. However, the transistor’s genesis remains poorly understood. Many received accounts associate transistor invention closely with a small group of Bell Labs scientists during the 1947-1948 period. This paper argues that such a view is too narrow. Rather, the transistor – as a solid-state amplifier – emerged over a period of several decades starting with early observations of anomalous amplification in semiconductor crystals and early device designs during the 1910s and 1920s. Other types of relevant knowledge evolved in the form of advances in solid-state physics and materials processing techniques during the 1930s and early 1940s. Bell Labs identified, absorbed, evaluated, and integrated such diverse but interrelated knowledge streams – making Bell Labs appear much more like a systems integrator than the prototypical closed innovation organization it is often portrayed as. The Bell Labs transistor effort was both mission- and device-oriented with the specific goal of turning existing but imperfect solid-state amplifier designs into reliable substitutes for vacuum tubes – as such the research program is better described as applied industrial research rather than basic research. Through its systems integration activities, Bell Labs catalyzed a qualitative shift in the hitherto fragmented semiconductor field, enabling greater resource allocation and intensified research activity, as reflected in a hike in publication growth rates and the later introduction of marketed products. Thus expanded research activity eventually led to the 1959 MOS-FET design as the transistor’s dominant design used in large-scale dissemination such as in modern computer chips. Consequently, I propose to view the transistor as an emerging invention – in contrast to a discrete or singular one – with an emergence period spanning several decades. I propose to distinguish between an exploration phase (~1920-1945), a consolidation phase (1945-1950), and a maturation phase (1950-) whereas the intermediate consolidation phase represents a topological transition as is characteristic of emerging fields. Another emphasis of this article lies on the role of informal knowledge in the invention process. In the transistor case, such informal knowledge included patent specifications with proposed device designs, amateur radio magazine articles with reported anomalies, and oral anecdotes in practitioner circles describing experimental configurations of interest. This research asserts that such kinds of informal knowledge played an important role early on in the invention process as they guided both early research campaigns and managerial decisions, including at Bell Labs.

Ku-band 360-W Pulsed Solid-State Power Amplifier with Excellent Comprehensive Performance

A design method of solid-state amplifier based on hybrid power-combining technique is presented in this paper. Also a 360-W pulsed solid-state power amplifier (PSSPA) constituted of 32 monolithic-microwave integrated-circuit power amplifiers (MMIC PA) operating in Ku band is designed successfully using this method. The PSSPA mainly consists of three stages of power-combining circuits and one stage of Wilkinson power-amplify module array. The power-combining circuits are respectively based on rectangular waveguide, coaxial line and microstrip line. The proposed combiner structures have the advantages of high power capacity, high power-combining efficiency and easy heat sink design. The measured results indicated that, in the frequency range of 15.5 GHz-16.5 GHz, the average output power is 362 W and the average active power-combining efficiency is 86.95%.

Push–Pull Class $\Phi _{\text{2}}$ RF Power Amplifier

The Class $\Phi _\text{2}$ /EF $_{\text{2}}$ amplifier is an attractive topology for high-voltage and high-frequency power conversion because of the high efficiency, reduced device voltage stress, simplicity of gate driving, and load-independent ZVS operation. Due to many degrees of freedom for tuning, previous studies can only solve the single-ended $\Phi _\text{2}$ circuit using numerical methods. This work focuses on improving the design and operating characteristics of a push–pull $\Phi _\text{2}$ amplifier with a $T$ network connected between the switch nodes, or a PPT $\Phi _\text{2}$ amplifier. The PPT $\Phi _\text{2}$ amplifier has less circulating energy and achieves higher cutoff frequency $f_{T}$ than other $\Phi _\text{2}$ /EF $_{2}$ circuits. We, then, present a series-stacked input configuration to reduce the switch voltage stress and improve the efficiency and power density. A compact 6.78-MHz, 100-V, 300-W prototype converter is demonstrated that uses low-cost Si devices and achieves 96% peak total efficiency and maintains above 94.5% drain efficiency across a wide range of voltage and power. Together with the advances in wide-bandgap semiconductors and magnetic materials, the PPT $\Phi _\text{2}$ circuit opens more possibilities for the state-of-the-art performance of solid-state RF amplifiers in high-frequency, high-power applications, including wireless charging for electric vehicles, plasma RF drives, and nuclear magnetic resonance spectroscopy.

A 150-kW Pulse Solid-State Amplifier for Radio Frequency Quadrupole Application

The development of a four vane 3-MeV radio frequency quadrupole is under progress at Raja Ramanna Centre for Advanced Technology, as part of the Indian facility for spallation source. This quadrupole will be powered by four identical 150-kW solid-state amplifiers, each operating at 325 MHz. This article describes the design details, rigorous testing, and measured results of the first such constructed amplifier and its constituent components. Its output power is 150 kW, with variable pulsewidth from 1 to 5 ms, at 50 Hz of pulse repletion rate. Its pulse amplitude droop measured at 1 ms is 0.46 dB. The phase variation around an average value, measured within a single pulse at 1 ms, is less than 2.7°. Its pulse-to-pulse amplitude stability and phase stability are ±0.1 dB and ±2°, respectively. Its main features are its modular and scalable design architecture, comprising of multiple extended continuous class F 1.5-kW amplifiers, energy-efficient two-tier radial power dividers as well as combiners, compact dual-channel power sensors, and aperture-coupled directional couplers.

A novel Ka-band chirped-pulse spectrometer used in the determination of pressure broadening coefficients of astrochemical molecules

A novel chirped-pulse Fourier transform microwave (CP-FTMW) spectrometer has been constructed to cover the Ka-band (26.5 GHz-40 GHz) for use in the CRESUCHIRP project, which aims to study the branching ratios of reactions at low temperatures using the chirped-pulse in uniform flow technique. The design takes advantage of recent developments in radio-frequency components, notably, high-frequency, high-power solid-state amplifiers. The spectrometer had a flatness of 5.5 dB across the spectral range, produced harmonic signals below -20 dBc, and the recorded signal scaled well to 6 × 106 averages. The new spectrometer was used to determine pressure broadening coefficients with a helium collider at room temperature for three molecules relevant to astrochemistry, applying the Voigt function to fit the magnitude of the Fourier-transformed data in the frequency domain. The pressure broadening coefficient for carbonyl sulfide was determined to be (2.45 ± 0.02) MHz mbar-1 at room temperature, which agreed well with previous measurements. Pressure broadening coefficients were also determined for multiple transitions of vinyl cyanide and benzonitrile. Additionally, the spectrometer was coupled with a cold, uniform flow from a Laval nozzle. The spectrum of vinyl cyanide was recorded in the flow, and its rotational temperature was determined to be (24 ± 11) K. This temperature agreed with a prediction of the composite temperature of the system through simulations of the experimental environment coupled with calculations of the solution to the optical Bloch equations. These results pave the way for future quantitative studies in low-temperature and high-pressure environments using CP-FTMW spectroscopy.

Stimulated Generation of Magnetrons powered below the Self-Excitation Threshold Voltage

Modern CW or pulsed superconducting accelerators of megawatt beams require efficient RF sources controllable in phase and power. Typically, the costs of the RF sources and their operation are a significant part of the total cost for large-scale projects. The efficiency of the traditional RF sources (klystrons, IOTs, solid-state amplifiers) is lower in comparison to magnetrons and the cost of RF power per Watt is significantly higher. Therefore the magnetron-based controlled in phase and power RF sources could significantly reduce the capital and operation costs of ADS and SNS like projects or, e.g., the Electron-Ion Collider projects unlike the traditional RF sources. Currently, a number of works suggests the use of magnetrons controlled by a resonant injected (injection-locking) RF signal instead of traditional RF sources. We developed a new approach to controlling magnetrons for superconducting accelerators with megawatts beams In the presented work we describe an innovative technique producing the “stimulated” RF generation of magnetrons powered below the self-excitation threshold voltage. This was predicted and substantiated by a recently developed kinetic (electrodynamic) model of magnetron operation. The technique allowing operation in CW and pulse modes has been experimentally verified and studied. It allows stable, controllable in phase and power operation of magnetrons providing efficiency higher than other types of RF power sources. The technique does not require high voltage pulse modulators for a pulsed RF generation. It also looks to be a promising opportunity to improve magnetron reliability and extend life time. Measured characteristics of the developed technique, its experimental verification and verification of the kinetic model briefly presented in the text are discussed in our work.

Theoretical study on beam quality and thermal stability in solid-state zigzag tube laser amplifier

Compared to zig-zag solid-state slab lasers, zig-zag solid-state tube lasers (SSZTLs) exhibit significant potential in beam quality improvement and output power enhancement. However, the progress of SSZTLs still faces enormous challenges due to the lack of effective control of beam quality. We first developed a comprehensive model for analyzing the output beam quality of zig-zag tube lasers by taking both the fabrication and alignment errors and thermal effects into consideration. The primary factors degrading the beam quality and thermal stability of the SSZTLs were analyzed in detail, and a self-correction method based on the complementary optical path was further proposed and analyzed theoretically to effectively improve the beam quality and thermal stability of the SSZTLs. The results show that this method can not only effectively correct the off-axis aberrations but also mitigate the depolarization loss that arises from the thermal instability of the SSZTLs. This work can provide a reference in the beam control and applications of SSZTLs.

A Solid-State Charge Detector With Gain Calibration Using Photocurrent

We describe a charge detector that utilizes a highgain, differential solid-state amplifier with active reset and a novel technique to measure the gain using a custom optoelectronic system. Implemented in a 180-nm complementary metal-oxide- semiconductor (CMOS) process, the amplifier realizes a high gain of 8.9 μV/e- and single-pass rms noise of 475e- for 10-ms time interval with a 300-kHz low-pass filter corner. Operating at a sampling frequency of 10 kHz, the active reset extends the dynamic range of the detector. The amplifier is the first instance of a charge detector that combines a differential topology, active reset, and small feedback capacitors for lownoise, high-gain, high-dynamic-range, and robust operations. The proposed optoelectronic test system injects an adjustable input photocurrent as low as 33 pA to precisely quantify the detector's gain without the need for a known calibration capacitance. The amplifier is directly wire-bonded to a PCB that has a built-in 1-cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> Faraday cup. The gain and noise performance have been characterized for a range of input capacitance, and the results show good agreement with simulations. The test system additionally demonstrates the ability to inject a time-varying input at the picoamphere levels to characterize the dynamic response of the detector. An electrospray system confirms that the detector responds to free-space charge and that it can process an input as large as 56 000e <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> without saturation. The compact and high sensitivity design qualify the device for use in charge detection applications, such as mass spectrometry and space instruments.

Polarization ray tracing in thermally loaded solid-state laser crystals

A new ray tracing method for the propagation of electrical fields in inhomogeneous and weakly anisotropic media is presented. With this method, we can efficiently simulate the propagation of laser beams in solid-state laser amplifiers, which suffer from high thermal loads. As a result of this method, we can find optical compensation setups that significantly reduce the depolarization losses in high-power solid-state amplifiers. To the best of our knowledge, we theoretically demonstrate for the first time that [100]-cut YAG crystals reduce the depolarization by more than a magnitude in comparison to [111]-cut crystals while achieving an overall better beam quality at the same time.

Development of fundamental power couplers for 166.6 MHz superconducting quarter-wave beta = 1 proof-of-principle cavities.

Superconducting 166.6 MHz β = 1 cavities of quarter-wave geometry have been chosen for a high energy photon source, a 6 GeV diffraction-limited synchrotron light source currently under construction in Beijing. Five cavities will provide the required 5.4 MV radio frequency (rf) voltage and 900 kW beam power. Each cavity will be equipped with one fundamental power coupler (FPC), delivering a minimum rf power of 180 kW to the beam. A 50 Ω coaxial structure with one planar warm window was employed. Its location was carefully selected to avoid electron bombardments on the ceramic window due to potential cavity field emission while preserving the required strong coupling. Focusing on optimized heat loads, a compact geometry was pursued to allow assembly with the cavity in a class 10 clean room, thus minimizing contamination. Two prototype FPCs have been fabricated and examined with high power on room-temperature test stands. The couplers were tested up to 50 kW continuous wave (cw) limited by the available solid-state amplifier. The rf conditioning was conducted initially in travelling-wave mode and later in a standing-wave setup with the variable phase of the reverse wave. All rf surfaces were thus exposed to a high field equivalent to 200 kW cw traveling wave. Being the most critical component, the window-inner-conductor assembly was conditioned up to 150 kW at 650 MHz on a hybrid test stand. Multipacting barriers were encountered as predicted and can be processed by rf conditioning. The design, fabrication, and high-power tests of the first 166.6 MHz FPCs are presented.

Single-step port-reconfigurable cavity combiner with high efficiency

Solid-state (SS) amplifiers present many benefits and advantages that make this technology a good candidate to substitute traditional vacuum technology amplifiers. The evidence is that many large scientific facilities are upgrading their radiofrequency (RF) power systems, replacing tetrodes or IOTs (Inductive Output Tubes) by SS amplifiers. Following this tendency, SS technology has been selected for the RF Power System of IFMIF-DONES (International Fusion Materials Irradiation Facility – DEMO-oriented Neutron Source). One of the current challenges in SS amplifiers is focused on achieving high efficiency in the power combination. This paper introduces a promising RF power combination technique for the reduction of the combination losses. It consists of a resonant cavity combiner, which can combine in only one step the power of a large number of power inputs with high efficiency. The design, fabrication, and experimental validation of a prototype cavity combiner will be presented. The objective is to develop an industrial design for the large-scale production that will be demanded by the IFMIF-DONES RF Power System.

X-Band Amplifier for the PAL-XFEL

Recent X-ray free electron lasers based on a high-energy high-current linear accelerator, such as the Pohang Accelerator Laboratory (PAL-XFEL) uses a third harmonic radio-frequency (RF) linearizer system to improve the laser's longitudinal beam quality. Because the X-ray free electron laser at the PAL-Xfel uses 2856 MHz RF accelerators, we realized a RF linearizer of 11.424 GHz which afforded a 50 MW RF power by using a SLAC X-band klystron. Operation of the X-band klystron required an X-band amplifier with a 1 kW level at the specified frequency of 11.424 GHz. We tested two types of X-band amplifier, a traveling wave tube amplifier and a solid state amplifier. In this work, we present the test results and discuss the features, especially focusing on the X-band solid state amplifier.

High gain fiber-solid hybrid double-passing end-pumped Nd:YVO4 picosecond amplifier with high beam quality**Project supported by the National Natural Science Foundation of China (Grant Nos. 61675009 and 61325021) and Key Program of Beijing Municipal Natural Science Foundation, China (Grant No. KZ201910005006).

We propose a fiber-solid hybrid system which consists of a semiconductor saturable absorber mirror (SESAM) mode-locked fiber seed with a pulse width of 10.2 ps and a repetition rate of 18.9 MHz, a two-level fiber pre-amplifier and a double-passing end-pumped Nd:YVO4 amplifier. In the solid-state amplifier, to enhance the gain and the extraction efficiency, a specially designed structure in which the seed light passes through the gain medium four times and makes full use of population inversion is used as the double-passing amplifier. Besides, the beam filling factor (the ratio of the seed light diameter to the pump light diameter) and the thermal lens effect of the double-passing amplifier are considered and its optical-to-optical conversion efficiency is further improved. To preserve the beam quality of the double-passing amplifier, a new method of spherical-aberration self-compensation based on the principles of geometrical optics is used and discussed. Our system achieves a maximum average power of 9.5 W at the pump power of 28 W, corresponding to an optical-to-optical efficiency of 27%. And the beam quality factor M2 reaches 1.3 at the maximum output power.

Role of Sm&lt;sup&gt;3+&lt;/sup&gt; on Mn Nanoparticles Embedded Zinc Tellurite Glasses Absorption and Luminescence Characteristic

Enhancing the optical performance of rare earth doped binary inorganic glasses is an ever-demanding quest. Samarium (Sm3+) doped zinc tellurite glasses containing Manganese (Mn) nanoparticles (NPs) with composition (59-x)TeO2-20ZnCl2-10ZnO-10Li2O-1Sm2O3-(x)Mn3O4, where x = 0 to 0.06 mol% are prepared by melt quenching technique. The role played by Mn NPs in enhancing the optical behaviors are analyzed and discussed. The XRD patterns confirm the amorphous nature of the glass. The UV-Vis-NIR spectra reveal seven prominent absorption bands of Sm3+ ions. The photoluminescence spectra display four peaks corresponding to 4G5/2→6H5/2, 4G5/2 →6H7/2, 4G5/2→6H9/2 and 4G5/2 →6H11/2 transitions. An enhancement in the luminescence intensity is observed up to 0.05 mol% concentration of NPs and the intensity quenches beyond it. The enhancement is attributed to local electric field effect of NPs in the proximity of Sm3+ ion. Our results on improved optical response via precise control of NPs contents may be useful for the development of solid state lasers and amplifiers.

Femtosecond CPA hybrid laser system with pulse-on-demand operation.

In this manuscript we present a true pulse-on-demand concept of a hybrid CPA laser system, consisting of a chirped-pulse fiber amplifier and an additional solid-state amplifier, capable of generating femtosecond pulses on demand without an external optical modulator/shutter. Pulse-on-demand operation is achieved by introducing idler pulses with a few nanoseconds duration and selectively switching between the femtosecond and idler pulses. The idler pulses are used to maintain a constant population inversion in the fiber amplifier as well as in the solid-state amplifier. Second harmonic generation (SHG) unit then effectively filters out the idler pulses due to their low peak power, leaving only a stable femtosecond pulse train. This concept is demonstrated on a CPA hybrid system that can generate pulses with up to 200 µJ at 515 nm with a pulse duration under 450 fs. As there is no optical modulator at the laser output, the presented concept also enables further power scaling.

Amplified spontaneous emission and optical gain characteristics of sexithiophene single crystals

This paper reports optical properties of a single crystal thiophene/phenylene co-polymer 5,5ʺʺ'-diphenyl-2,2′:5′,2ʺ:5ʺ,2ʺ′:5ʺ′,2ʺʺ:5ʺʺ, 2ʺʺ'-sexithiophene (P6T). The P6T crystals demonstrate high charge carriers’ mobility and large photoluminescence quantum efficiency (PLQE). Herein, the stimulated emission of P6T is studied within wide range of pump energies –refers to energy per pulse – (from 19 ± 0.5 μJ/cm2 to 64.2 ± 0.5 μJ/cm2) through amplified spontaneous emission (ASE) measurements by using Nd-YAG femtoseconds tunable pulsed laser at 445 nm excitation wavelength (λexc). ASE measurements exhibit lower threshold energy density (Eth) i.e., ~26 ± 0.5 μJ/cm2 which confirms optical amplification in P6T at 632 nm emission wavelength. The ASE characteristics of P6T are also studied as a function of different λexc ranging from 425 to 475 nm to find the wavelength for optimum amplification. It is observed that the maximum optical amplification for P6T occurs at a λexc of 445 nm. These crystals exhibit large optical gains which are measured to be 69 cm−1, 53 cm−1 and 29 cm−1 at excitation energies of 91 ± 0.5 μJ/cm2, 66 ± 0.5 μJ/cm2 and 43 ± 0.5 μJ/cm2, respectively. PL measurements of P6T crystals demonstrate large value of the PLQE ~57.36%. This study suggests the potential of P6T single crystal as one of the good candidates among high optical gain materials of its kind for its possible applications in solid-state lasers, photodetectors and optical amplifiers.

Spatiotemporal characterization of laser pulse amplification in double-pass active mirror geometry

Abstract We present a spatiotemporal model of pulse amplification in the double-pass active mirror (AM) geometry. Three types of overlap condition are studied, and the spatiotemporal scaling under the four-pulse overlapping (4PO) condition is fully characterized for the first time, by mapping the temporal and spatial segments of beam to the instantaneous gain windows. Furthermore, the influence of spatiotemporal overlaps on the amplified energy, pulse distortion and intensity profile is unraveled for both AM and zigzag configurations. The model, verified by excellent agreement between the predicted and measured results, can be a powerful tool for designing and optimizing high energy multi-pass solid-state laser amplifiers with AM, zigzag and other geometries.

РАСПРЕДЕЛИТЕЛЬНО-СУММИРУЮЩИЕ СИСТЕМЫ ТВЕРДОТЕЛЬНЫХ ПЕРЕДАЮЩИХ УСТРОЙСТВ СОВРЕМЕННЫХ РЛС

One of the most important components of the radar system, which determines its potential characteristics, is the transmitting device. It is known that the advantage of constructing transmitting devices based on the principle of coherent summation of the power of solid-state amplifier modules is that they allow obtaining the required output power level and ensuring the operation of the radar in the "smooth failure" mode with the possibility of prompt replacement of faulty amplifier modules during operation. At the same time, an urgent task is to increase the output power level of the transmitting device by reducing losses in its microwave path, caused by the spread of the amplitudes and phases of the summed signals. This article provides a brief overview of materials from open Russian and foreign sources on methods for summing the power of microwave oscillations, as well as possible ways to implement combiners/dividers of power of solid-state amplifying modules, on the basis of which the output stages of transmitting devices of modern radar systems are built. The advantages and disadvantages of Wilkinson combiners, waveguide traveling wave combiners, as well as problems arising in their development are discussed. The main issues related to increasing the efficiency when summing the power of several amplifying modules of the same type of the transmitting device are considered. It is shown that the choice of the summation/division scheme and its constructive implementation are determined by the range of operating frequencies, the output pulse and average power of the transmitting device, and the permissible weight and dimensions. The rationality of methods for obtaining the required output power in each specific case is analyzed, including the most promising ones based on special correction schemes that reduce the phase errors of the distribution-summing system.

Pulses on Demand in Fibre and Hybrid Lasers

This paper presents an investigation of pulse-on-demand operation in fibre and hybrid lasers. Two methods for efficient gain control that enable the generation of laser pulses at arbitrary times with controlled pulse parameters are presented. The method of direct modulation of the pump power in the high-power laser oscillator is shown to generate pulses with a duration in the nanosecond range, with repetition rates varying during operation from a single shot to over 1 MHz. An advanced method using a combination of marker and idler seeding a fibre amplifier chain is investigated. Such a system can easily achieve repetition rates of several tens of MHz. The lasers’ performances were successfully tested in a real environment on an industrial platform for laser transfer printing. Similar concepts were used for a laser source with ultrashort laser pulses (femtosecond range) on demand by using a mode-locked seed as a source and a solid-state amplifier to achieve high pulse energy and peak power.

The commission of the home-made 500MHz, 80kW solid-state amplifier in NSRRC

Solid-state for high power RF application is an attracting and interesting technology which is now become popular in accelerator field. To adopt and master such technique, a 500MHz, 80kW solid-state amplifier is thus developed in NSRRC. The amplifier is consisted of 100 900W amplifier modules which are driving by identical modules. Each module contains input and output directional couplers and status monitoring circuits. To have longer life time and better performance, the RF power transistors are integrated with water cooled heat sink directly. In such a way, the transistors have higher output power and better efficiency. The RF power of each module is combined through coaxial combiner while its DC power is provided by parallel connected DC power supplies which can provide better redundancy and reliability. The home-made solid-state amplifier is demonstrated to have quite high quality RF power and reliability with acceptable power combination efficiency.