Monolithic Resonator Research Articles

Absolute in situ measurement of surface dangling bonds during a-Si:H growth

Hydrogenated amorphous silicon (a-Si:H) is regarded as a model system in mechanistic studies of amorphous semiconductor film growth, where the key reactive site is generally considered to be a surface “dangling bond.” Employing an ultrahigh-Q (≈1010) monolithic optical resonator, the authors probe the creation of dangling-bond defects during growth of a-Si:H from a predominantly SiHx (x=0–3) radical flux by detecting the associated near-IR subgap absorption with evanescent wave cavity ringdown spectroscopy. They find the apparent dangling-bond creation rate [(5±3)×1012cm−2s−1] and steady-state surface density [(5±2)×1011cm−2] to be considerably lower than expected from dangling-bond-based growth mechanisms.

Coplanar monolithic resonator for X-ray and synchrotron radiation

A scheme of a three-block monolithic X-ray resonator with Si \((04\bar 4,40\bar 4)\)-configuration single crystal for NiKα2 and synchrotron radiation is proposed and realized experimentally. Specialties and advantages of the proposed scheme are given. It is shown that using asymmetric Bragg reflections makes possible to solve one of the basic problems of X-ray resonators, that of the input of radiation into the resonator and creation of the lossless cycle. The technology of fabrication of the resonator is described and the problems of raising the efficiency of its operation are considered.

Direct Modulation Characteristics of Composite Resonator Vertical-Cavity Lasers

We report the small-signal modulation characteristics of a monolithic dual resonator vertical cavity surface emitting laser. The modulation response is described by a system of rate equations with two independent carrier populations and a single longitudinal optical mode. The independent optical overlaps and differential gains of the two active regions can each be adjusted to maximize the output response. We show that under certain conditions, the composite resonator may achieve a higher bandwidth than a single cavity laser with the same photon density. We find the relaxation oscillation frequency to depend mainly on the total photon density and not the individual currents in the two cavities. With appropriate current injection, the composite resonator laser achieves a maximum -3-dB bandwidth of 12.5 GHz and a maximum modulation current efficiency factor of approximately 5GHz/ma1/2

Characterization of flexible RF microcoils dedicated to local MRI

In magnetic resonance imaging (MRI), the electrical performance of the RF coil is critical to achieve sufficient signal to noise ratio (SNR), especially when microscopic structures [about (100 μm)3] have to be observed. In this field of application, we have developed a device (microcoil) based on the original concept of monolithic resonator, dedicated to superficial region imaging (human skin) or small animal imaging. This paper presents the developed process based on micromoulding. Flexible thin films of polymer have been used as dielectric substrate so that the microcoil could be form-fitted to non-plane surfaces. First, electrical characterizations of the RF coils have been performed. The results were compared to the expected values. A flexible RF coil of 15 mm diameter was then used to perform proton MRI of a saline phantom. When the coil was form-fitted to the phantom surface, a maximum SNR gain of 2 was achieved with respect to identical but plane RF coil. Finally, the flexible coil was used to perform MRI in vivo with high spatial resolution on a mouse using a small animal dedicated scanner operating at 2.35 T.

High slope efficiency measured from a composite-resonator vertical-cavity laser

We report high differential slope of the light versus current (L-I) characteristic in excess of 400% external quantum efficiency from a monolithic dual resonator vertical-cavity surface-emitting laser. The additional optical cavity of the composite resonator can provide gain or loss to the distributed laser mode, depending on the bias conditions. We describe the factors contributing to the internal optical loss, and present a qualitative model for the L-I characteristic. With sufficient current injected into the top cavity, the composite-resonator vertical-cavity laser achieves over 6 W/A of differential slope efficiency from threshold to greater than 1 mW of output power, which may be applicable for analog optical data links.

Monolithic Above-IC Resonator Technology for Integrated Architectures in Mobile and Wireless Communication

This paper demonstrates the feasibility of an above-IC bulk acoustic wave technology for wireless applications. A double-lattice bulk acoustic wave (BAW) filter with balanced input and output has been designed and integrated as a post-process directly above 0.25 /spl mu/m BiCMOS wafers comprising RF circuits. This filter, featuring moderate insertion loss of -3dB and extreme out-of-band rejection (>-50 dB) is used in a simplified RF front-end receiver for the WCDMA standard, as well as in a new type of filtering LNA comprising two broadband amplifiers and one BAW filter.

Quasi-Ice Monolayer on Atomically Smooth AmorphousSiO2at Room Temperature Observed with a High-Finesse Optical Resonator

The structure of an H(2)O monolayer bound to atomically smooth hydroxylated amorphous silica is probed under ambient conditions by near-infrared evanescent-wave cavity ring-down absorption spectroscopy. Employing a miniature monolithic optical resonator, we find sharp (approximately 10 cm(-1)) and polarized (>10:1) vibration-combination bands for surface OH and adsorbed H(2)O, which reveal ordered species in distinct local environments. Indicating first-monolayer uniqueness, the absorption bands for adsorbed H(2)O show intensity saturation and line narrowing with completion of one monolayer. Formation of the ordered H(2)O monolayer likely arises from H bonding to a quasicrystalline surface OH network.

A GaInAsP-InP double-ring resonator coupled laser

A monolithic single-mode GaInAsP-InP double microring resonator coupled laser is demonstrated for the first time. The laser comprises two passive ring resonators, semiconductor optical amplifiers in the bus waveguides, and 3-dB codirectional couplers. The laser has an output power of 0.5 mW with a sidemode supression ratio of >35 dB. The tunability is demonstrated using integrated platinum resistors on top of the waveguides in the rings.

Monolithic Fabry-Perot resonator for the measurement of optical constants in the terahertz range

A prism-shaped monolithic Fabry-Perot resonator is shown to allow absorption measurements of liquid samples in the terahertz wave range. As the radiation source a backward-wave oscillator was chosen for its tunable, highly monochromatic, continuous wave. The resonator is made of high-resistivity silicon, with two surfaces acting as partial mirrors and forming the cavity, while a third one contributes with a total internal reflection. When a liquid sample is placed on this latter surface the total reflection is attenuated and the finesse of the resonator decreases, providing absorption information about the sample. The measurement method relying on Fourier processing of the signal, as well as experimental data are presented.

Terahertz cavity-enhanced attenuated total reflection spectroscopy

We realized cavity-enhanced absorption spectroscopy in the terahertz spectral region by combining multilayer mirrors with an attenuated total reflection technique. Using this technique, we were able to observe an absorbance of biological samples with a minimum detectable concentration as low as 8×10−10mol∕mm2. The absorbance between 75cm−1 and 115cm−1 was measured using a monolithic resonator of high-purity silicon. We demonstrate that the sensitivity of the attenuated total reflection design is significantly improved by adding multilayer mirrors for the THz region.

Mechanical effect of gold nanoparticles labeling used for biochemical sensor applications: A multimode analysis by means of SiNx micromechanical cantilever and bridge mass detectors

The effect on mechanical properties of monolithic SiNx micromechanical cantilever and bridge by the adsorption of gold colloids is reported by measuring their resonance frequency shifts. It is experimentally demonstrated that higher resonance modes are more sensitive to the added mass than the fundamental resonance mode leading to increased sensitivity. This is even more significant with monolithic SiNx bridge resonators due to the tensile stress within the SiNx layer. Indeed, resonance frequencies are about ten times higher than calculation without taking into account the tensile stress which was estimated at 500 MPa. Another important result is that the adsorbed colloids do not produce significant change in the stiffness of the SiNx micromechanical resonators. Hence, it is pointed out that only the added mass of Au colloid contributes to the change in the mechanical characteristics of the resonators. Sensitivities up to 20 Hz/pg can be obtained with a minimum detectable density of gold colloids about 2.6×10−2 nanoparticles/μm2.

Acoustic quality factor of aluminium and selected aluminium alloys from 50 mK to 300 K

Abstract The amplitude-independent quality factors ( Q s) of polycrystalline aluminium of 99.999 wt% purity, and the commercial aluminium alloys 2024, 6061 and 7075 have been measured in the temperature range 50 mK–300 K. Data were obtained at about 1 kHz from a torsional mode of machined monolithic mechanical resonators. The as-machined alloys exhibited maximum Q s of 1.5 to 9.5 million. The annealed alloys exhibited maximum Q s from 4.3 to 7.4 million. After several weeks at room temperature, substantially higher Q s were observed in all of the annealed materials, as compared to values obtained within a few days subsequent to the thermal treatment. Nevertheless, the maximum Q s were appreciably lower than those which have been measured in aluminium–magnesium alloys. Three loss peaks were observed in the aluminium, and a single peak in two of the alloys, even after annealing. The temperature dependence of the shear moduli was also obtained. This study is part of the continuing effort in this laboratory to evaluate the acoustic loss of high- Q materials at low temperatures, of particular interest for the construction of sensitive detectors of gravitational radiation.

Proposed test of the time independence of the fundamental constantsαandme/mpusing monolithic resonators

A novel method is proposed for a laboratory test of the time independence of the fine-structure constant and of the electron to proton mass ratio, employing only electromagnetic resonators. For a resonator made out of a dielectric ionic or molecular crystal, the resonance frequencies depend on the product ${\ensuremath{\alpha}}^{2}\sqrt{{m}_{e}{/m}_{p}}$ through the index of refraction. A test of the time independence of $\ensuremath{\alpha}$ and ${m}_{e}{/m}_{p}$ can be performed by a search for a long-term change in the difference of two resonance frequencies exhibiting different dispersion. The method can be advantageously implemented with a single resonator. The prospects of implementation using optical resonators, systematic effects, and experimental requirements for a test at the level of $4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}/\mathrm{yr}$ relative variation in $\ensuremath{\alpha}$ or ${m}_{e}{/m}_{p}$ are discussed. On the experimental side, birefringent monolithic sapphire optical resonators with high-reflectivity mirrors are fabricated and characterized. The measurements of optical materials with ultralow absorption loss (ppm/cm level), required for the proposed method, are also reported.

The history of ceramic filters

The history of ceramic filters is surveyed. Included is the history of piezoelectric ceramics. Ceramic filters were developed using technology similar to that of quartz crystal and electro-mechanical filters. However, the key to this development involved the theoretical analysis of vibration modes and material improvements of piezoelectric ceramics. The primary application of ceramic filters has been for consumer-market use. Accordingly, a major emphasis has involved mass production technology, leading to low-priced devices. A typical ceramic filter includes monolithic resonators and capacitors packaged in unique configurations.

Frequency-temperature compensation in Ti/sup 3+/ and Ti/sup 4+/ doped sapphire whispering gallery mode resonators

A new method of compensating the frequency-temperature dependence of high-and monolithic sapphire dielectric resonators near liquid nitrogen temperature is presented. This is achieved by doping monocrystalline sapphire with Ti(3+) ions. This technique offers significant advantages over other methods.

Zeolite-Dye Microlasers

We present a new class of micro lasers based on nanoporous molecular sieve host-guest systems. Organic dye guest molecules of 1-Ethyl-4-(4-(p-Dimethylaminophenyl)-1,3-butadienyl)-pyridinium Perchlorat were inserted into the 0.73-nm-wide channel pores of a zeolite AlPO$_4$-5 host. The zeolitic micro crystal compounds where hydrothermally synthesized according to a particular host-guest chemical process. The dye molecules are found not only to be aligned along the host channel axis, but to be oriented as well. Single mode laser emission at 687 nm was obtained from a whispering gallery mode oscillating in a 8-$\mu$m-diameter monolithic micro resonator, in which the field is confined by total internal reflection at the natural hexagonal boundaries inside the zeolitic microcrystals.

Continuous-wave, all-solid-state, single-frequency 400-mW source at 589 nm based on doubly resonant sum-frequency mixing in a monolithic lithium niobate resonator

Sum-frequency mixing of two cw single-mode Nd:YAG lasers in a doubly resonant congruent lithium niobate resonator generated two TEM(00) beams of single-frequency 589-nm radiation. The primary beam had a power of 400 mW and the secondary beam of approximately 15 mW by use of 320 mW of 1319-nm and 660 mW of 1064-nm Nd:YAG radiation incident on the lithium niobate resonator. This corresponds to an optical power conversion efficiency of more than 40%.

X-Ray Resonators

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Temperature variation of the refractive index of potassium niobate

Use was made of a novel Fabry–Pérot interferometer technique to determine the variation of refractive index with temperature (∂n/∂T) of a potassium niobate crystal with a GaAlAs diode laser. The transverse intensity distributions of the laser transmitted through the crystal were found to be temperature dependent, and the ∂n/∂T values along crystallographic b and c axes were determined to be −4.5×10−5 and 6.1×10−5 °C−1, respectively. The temperature changes required for tangential tuning from transverse mode TEMqmn to TEMqm+1n and sagittal tuning from TEMqmn to TEMqmn+1 were found to be 0.29 and 1.27 °C, respectively, when the laser was polarized along the b axis. When the laser polarization was along the c axis, the tangential and sagittal tunings were found to be 0.10 and 0.54 °C, respectively. These differences between the tangential and sagittal directions indicated that the monolithic ring resonator used was indeed asymmetric.

82% Efficient continuous-wave frequency doubling of 106 μm with a monolithic MgO:LiNbO_3 resonator: errata

We describe a frequency-doubling monolithic standing-wave resonator made of MgO:LiNbO(3) with dielectric mirror coatings for impedance matching near 100 mW input power and near-optimum nonlinear coupling. An external conversion efficiency of 82% has been achieved.