Full-wave analysis of waveguide-to-microstrip transitions for millimeter wave applications

A full-wave solution is presented for the waveguide to microstrip transition. The exact Green's function of the transition is used in a moment method procedure. The behavior of the microstrip transition to a rectangular waveguide is studied with respect to the critical dimensions of the microstrip width, length and backshort location. The convergence characteristics of the full wave analysis method are investigated, along with the current distribution and the input impedance. Results given for the return loss is compared with measurements.     

Doppler-free two-photon modulation transfer spectroscopy in sodium dimers

We performed an experiment to investigate modulation transfer spectroscopy in two-photon transition of Na₂ using a CW dye laser. Comparing with UV fluorescence detection, the signals obtained by modulation transfer spectroscopy have a very high S/N without the Doppler background problem and its line shape is in agreement with theoretical calculations.Project supported by National Natural Science Fund of ChinaPermanent address: Shanghai University of Technology, Shanghai 200072, People's Republic of China     

Self-broadening and shift of Doppler-free two-photon lines of Rb

The self-broadening and shift rates of 14 two-photon lines of the $\text{5}{}^2\text{S}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{?n}{}^2\text{D}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext><mtext>,</mtext><mtext>5</mtext><mtext>2</mtext>}}$ series and 8 lines of the $\text{5}{}^2\text{S}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{?n}{}^2\text{S}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ series of Rb were measured using thermionic detector and the technique of Doppler-free two-photon spectroscopy. The dependence of the broadening and shift of the lines on the principal quantum number is discussed and compared with experimental data for the Rb principal series lines and recent theoretical estimates.     

Doppler-free two-photon spectroscopy of the 2ν3 band of SF6

High-resolution spectroscopy of the 2ν₃ band of SF₆ is reported by means of Doppler-free two-photon transitions. Parts of spectra are measured with accuracy of 10⁻⁹. This technique applied to SF₆ should lead to an assignment of the spectra involved.     

Phonon-assisted two-photon transitions in semiconductors

The effect of the non-parabolicity of the energy bands on the indirect two-photon transition is theoretically studied. An expression for the absorption coefficient valid both near and far from the energy gap is given. Numerical results, compared with recent experimental data on AgCl, show that the dominant transition mechanisms are of the allowed-allowed type near and far from the edge.     

Radiative collisions and two-photon transitions

We explore the heuristic connections between laser-induced energy transfer in radiative collisions and a simple two photon transition involving two near-resonant fields.     

Detection of weak microwave and millimeter wave transitions in the C-O stretch state of methyl alcohol

In this work microwave and rum-wave techniques have been applied to measure accurate transition frequencies in the first excited C-O stretching state of methyl alcohol. The measured frequencies for the assigned transitions are in excellent agreement with those predicted from infrared (IR) and ground slate microwave and mm-wave combination differences. For the (nτK) = (031) state, transitions corresponding to asymmetry doublets were detected, yielding an accurate asymmetry splitting parameter.     

Far-infrared two-photon intraband transitions in n-InSb

Two-photon cyclotron resonance and two-photon shallow donor transitions have been excited by a high power pulsed D₂O laser emitting λ = 119 μm and 66 μm laser lines at the same time. Transitions involving the absorption of two 119 μm photons or simultaneously one 119 μm and one 66 μm photon were observed. Two-photon selection rules are discussed by a rigorous treatment of the symmetry of the free electron Hamiltonian.     

Collisional broadening and shift of Doppler-free two-photon thallium lines perturbed by rare-gas atoms

The extended Omont-Ueda-Kaulakys treatment of collisional effects on quasi-Rydberg states, in which the perturbation of the lower state is taken into account is applied to thallium-rare gas systems. The pressure broadening and shift coefficients of two-photon transitions in thallium involving the 6P_1/2 -n P_1/2,3/2 (n = 9-14) states are calculated and compared with experimental data obtained by Hermann et al. [Eur. Phys. J. D 1, 129 (1998)].     

Measurement of linewidth of two-photon Doppler-free optoacoustic signal and influence of collision broadening

A simple method of measuring linewidths of Doppler-free optoacoustic signals is introduced, and the influence of collision broadening on the linewidth of such optoacoustic signals is analyzed in this paper.     

Self-broadening of the Na 3S-5S and 3S-4D two-photon transitions

Self-broadening of the Na 3s-5s and 3s-4d two-photon transitions has been measured. The results agree with a calculation based on van der Waals interaction between excited and ground state Na atoms.     

Surface wave fields and power in millimeter wave integrated dipole antennas

In this paper simple closed form expressions of surface wave fields for microstrip dipoles on grounded substrates are presented. The surface power, radiated power and radiation efficiency are calculated. It is shown that the radiation efficiency decreases with the increase of substrate electrical thickness. Hence new type antennas are needed to radiate millimeter wave because of the effect of the surface waves in substrate.     

l-type doubling transitions in Δ states of OCS

Molecular beam electric resonance spectroscopy has been used to measure the l-type doubling transitions in carbonyl sulfide. Transitions in J = 4 to J = 20 have been observed for the (02²0) vibrational state and for J = 1 and J = 2 for the (03¹0) state. The data has been analyzed to give the v = 2 energy separation $\text{E}{}_{\mathrm{<mtext>\Delta </mtext>}}{}^0\text{- E}{}_{\mathrm{<mtext>\Sigma </mtext>}}{}^0\text{= ?5.7861(2) + 8.36(1) × 10}{}^{\mathrm{?5}}\text{J(J + 1)}\text{cm}{}^{\mathrm{?1}}$, and the vibrational dependence of q to be 86.52(9)(v₂ + 1) KHz. The dipole moment of the (02²0) vibrational state is 0.6936(3) D.     

Optoacoustic detection of Doppler-free two-photon resonances in the v2 bands of NH3

A new approach to infrared two-photon spectroscopy is described. An optoacoustic cell operating at low pressure is used to detect Doppler-free transitions excited by a conventional and a waveguide CO₂ laser. Beams from the two lasers are passed through the sample in opposite directions and an electric field tunes the transitions into resonance by molecular Stark effect. A few examples are discussed to illustrate the features and the sensitivity of the method.     

Polarization dependence of two-photon transitions in quantum wells

Summary We give explicitly the polarization dependence of two-photon subband-subband transitions in semiconductor quantum wells. We consider transitions from heavy-hole subbands as well as from light-hole subbands. We study the polarization dependence in the case of absorption of one photon having an energy of the order of the band gap and one having an energy of the order of the subband separation. We show that the absorption structure depends on the polarization of the low-energy photon. We also give, in the case of equal photons with in-plane linear polarizations, the dependence of the transition rate on the angle between the polarizations.     

Global optimization method in millimeter wave combiner

This paper describes an algorithm which can determine the global optima of the power combiner of solid-state millimeter wave resonator. The global optimization mehtod can determine a neighborhood of the global optima of an objective function and an estimation of the global optima. In this paper the objective function as follow: In the quasi-optical resonator, the objective function are the fundamental mode power, the fractional power of fundamental mode and the combining dfficiecy were done the objective functiona respectively, to calculate the global optima respectively. In the power combiner of solid-state millimeter wave source in rectangular waveguide cavity. the performance parameter are presentes by combining efficiency, tuning range, frequency drift, and FM noise were done the objective functions respectively. And to calculate the global optima respectively.