Low Optical Transmission Research Articles

An optical multiaccessor designed for a fiber-optic star-ring LAN

An optical waveguide-type multiaccessor for physically star and logically ring local area networks (star-ring LANs) has been manufactured. The multiaccessor has sufficient low optical transmission loss to bypass some failure nodes without an optical repeater. As the multiaccessor (eight-node-connection type) features are small size, 5 cm square by 0.5 cm thick, a smaller cable concentrator can be applied. The design method used for the multiaccessor to minimize total optical transmission loss caused by both signal interference loss and bypassing loss when failure nodes are bypassed in the star-ring LAN is described. The experimental results for the 32 Mb/s single-mode fiber-optic star-ring system show that at least three nodes can be continuously bypassed by using the multiaccessor with a coupling ratio of 0.5 and a bypass loss of 3 dB. As a result, highly reliable and inexpensive star-ring LANs can be designed with the multiaccessor. >

ChemInform Abstract: Effect of Grain Growth on Hot‐Pressed Optical Magnesium Fluoride Ceramics.

An optical MgF2 ceramic was hot-pressed at 838 to 983 K with 241-MPa pressure. The maximum mechanical strength (>180 MPa) developed in the resulting ceramic within the grain-growth range μ/μ0= 7 to 10, where μ is the grain size of the hot-pressed article and μ0 that of the starting powder. In the early stages of grain growth (μ/μ0<7), however, mechanical strength was directly proportional to grain size, which appeared to contradict the expectations of the Petch and Knudsen relations. Optical transmission was inversely proportional to grain size, especially in the visible wavelength. This study thus demonstrates a particular case in which increasing grain size promotes higher mechanical strength but lower optical transmission.

Effect of Grain Growth on Hot‐Pressed Optical Magnesium Fluoride Ceramics

An optical MgF2 ceramic was hot‐pressed at 838 to 983 K with 241‐MPa pressure. The maximum mechanical strength (&gt;180 MPa) developed in the resulting ceramic within the grain‐growth range μ/μ0= 7 to 10, where μ is the grain size of the hot‐pressed article and μ0 that of the starting powder. In the early stages of grain growth (μ/μ0&lt;7), however, mechanical strength was directly proportional to grain size, which appeared to contradict the expectations of the Petch and Knudsen relations. Optical transmission was inversely proportional to grain size, especially in the visible wavelength. This study thus demonstrates a particular case in which increasing grain size promotes higher mechanical strength but lower optical transmission.

Transmission and photoreflectance spectra in highly strained InGaAs-GaAs multiple quantum wells

Low temperature optical transmission spectra (TS) and room temperature photoreflectance (PR) spectra have been measured to investigate several In xGa 1− x AS GaAs strained multiple quantum wells (MQWs) grown by molecular beam epitaxy (MBE). Sharp PR features indicating excellent optical quality of these samples were observed. The excitonic transitions up to 3C-3H are observed. The notation nC-mH(L) is used to indicate the transitions related to the n-th conduction and m-th valence heavy (light) hole subbands. The band-to-band transitions are also observed in both TS and PR spectra, which, having step-like structure in TS spectra, are identified as 1C-1L transitions. The calculated transition energies, taking into account both the strain and the quantum well effects, are in good agreement with the TS and PR spectra. This shows that room temperature PR is a powerful and convenient tool to investigate the strained layer MQWs. By fitting the experimental results (TS and PR), a heavy-hole valence band discontinuity of 30% was obtained for 0.13 ≤ × ≤ 0.193. We conclude that the light holes are in the GaAs barrier region (Type II MQWs) and the light hole transition 1C-1L is a sensitive parameter in determining the band offset in GaAs GaAs strained layer MQWs.

Highly conductive and transparent zinc oxide films prepared by rf magnetron sputtering under an applied external magnetic field

Highly conductive films of zinc oxide have been prepared by rf magnetron sputtering deposition on a substrate suspended perpendicular to the target under an applied external magnetic field in pure argon gas. It is shown that a film with low resistivity (5×10−4 Ω cm) and high optical transmission (&amp;gt;85% between 400 and 800 nm) can be produced on low-temperature substrates with a relatively high deposition rate. The sheet resistance and Hall mobility of the film are 10 Ω/⧠ and 120 cm2/Vs respectively. The high conductivity is achieved by an increase in Hall mobility due to improved crystallization.

Preparation of conducting and transparent thin films of tin-doped indium oxide by magnetron sputtering

High-quality 800-Å-thick films of tin-doped indium oxide have been prepared by magnetron sputtering. It is shown that films with low resistivity (∼4×10−4 Ω cm) and high optical transmission (≳85% between 4000 and 8000 Å) can be prepared on low-temperature (40–180 °C) substrates with O2 partial pressures of (2–7)×10−5 Torr.

Refractive-index-adjustable SiO2-Ta2O5 films for integrated optical circuits

This report is about the preparation and the optical transmission loss of rf-sputtered SiO2-Ta2O5 films that are suitable for use as transmission media in integrated optical circuits. It is shown that the films, which can be produced with a refractive-index range from 1.46 to 2.08 at 6328 Å wavelength by suitably selecting the ratio of the target constituents, exhibit a low optical transmission loss of less than 0.8 dB/cm for the TE0 mode.

A simple method of making vacuum-tight coolable window seals for low temperature optical transmission cells

A simple method of making vacuum-tight coolable window seals for low temperature optical transmission cells

A simple method of making vacuum-tight coolable window seals for low temperature optical transmission cells

A means of sealing various optical materials to copper or glass apparatus has been devised. The seals have been tested under high vacuum between room temperature and 20°K, and should be satisfactory at still lower temperatures.