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We have built polarization stabilizer arrays of ultrathin liquid-crystal (LC) polarization controller (PC) arrays and a tap-type photodetector array on a fiber array. The ultrathin (35-μm-thick) LC cells are inserted into trenches cut across the fiber array, which is affixed to V grooves in a glass plate and are used to change the phase of 1.55-μm lights from 0.5 to 3.9π with the application of less than 3 Vrms. Two cascaded ultrathin LC cells, where the directions of alignment of the LCs are rotated by 45° relative to each other, are capable of converting light with an arbitrary input polarization to the transverse electric (TE) or transverse magnetic (TM) polarization. We fabricated a multichannel TE- and TM-polarization stabilizer of the previously mentioned 16-channel LC PC array and a feedback system made up of a multichannel tap-type photodetector array, sheet polarizer, and a computer and analog-to-digital converters. Feedback control was applied to maximize and minimize the tapped light, to convert an arbitrary input polarization to TM or TE output polarization, and stabilize it in the given state. [ABSTRACT FROM PUBLISHER]

A Pb1-xLax(ZryTiz)1-x4/O3 (PLZT) electrooptic ceramic variable-rotatable waveplate and a compact inline polarimeter have been used to develop a fast feed-forward-controlled module for the continuous and complete conversion of polarization. This requires the control of only two parameters: the direction θ and strength of the applied voltage V0. Feed-forward control speed is fast, taking only 24 μs. The chip plates were made by cutting T-shaped trenches into the four sides of a 500×400×300-μm3 PLZT chip and coating the trenches with electrodes. The PLZT waveplate is inserted into a 330-μm gap between thermally expanded core fibers. The input polarization states are monitored by a newly developed compact and fast inline polarimeter, which is placed in front of the polarization controller. The optimum θ and V0 values for the required conversion are calculated by a computer, and the corresponding voltages are then applied to PLZT waveplate. [ABSTRACT FROM PUBLISHER]

The degradation mechanism of a vertical-cavity surface-emitting laser (VCSEL) with an air-post structure is analyzed for stable optical parallel interconnection communication. It is clarified that the degradation is caused by the behavior of latent defects in the GaAs active layer. Decreasing the defects in the active region as well as decreasing the threshold current is important for obtaining a long-lifetime VCSEL [ABSTRACT FROM PUBLISHER]

We investigated the waveguide loss and transmission characteristics for optical interconnection using vertical-cavity surface-emitting lasers (VCSELs) and multimode polymeric waveguide circuits with crossings. The excess loss with 100 crossings is 2.2 dB when the image magnification from a VCSEL to a waveguide is 2.3. We obtained error-free (i.e., bit error rate <10-11) optical interconnection at 1.0625 Gbps regardless of the number of crossings or the magnification. These results suggest the practicality of large-scale optical interconnection between VCSEL-based smart-pixel chips using multimode waveguides with more than 100 crossings [ABSTRACT FROM PUBLISHER]

We demonstrate the polarization stability of 850-nm-wavelength vertical cavity surface-emitting lasers (VCSELs) grown on (311)B substrates under continuous-wave (CW) and dynamic operation. To clearly verify the polarization stability of VCSELs on (311)B substrates due to the anisotropic optical gain, the characteristics of both VCSELs on (311)B and (100) substrates were compared experimentally. Under CW operation, very small difference in both orthogonal polarization suppression ratio and the distribution of polarization direction was observed between VCSELs on (311)B and (100) polyimide-buried structures. On the other hand, significantly larger orthogonal polarization suppression ratio was obtained for VCSELs on (311)B substrates than those on (100) substrates under zero-bias modulation. Time-dependent orthogonal polarization suppression ratio measurements also showed that the orthogonal polarization suppression ratios of the VCSEL on (311)B substrates were more stable than those on (100) substrates. The data transmission characteristics also indicate large differences in the dependence of the bit error rate on bias current and the power penalty between polarization resolved and unresolved systems between VCSELs on (311)B and (100) substrates. The beneficial effect of the polarization stability of VCSELs on (311)B substrates due to their anisotropic optical gain is clearly demonstrated [ABSTRACT FROM PUBLISHER]

Analytical expressions are derived for the signal-to-noise ratio and resolution in the stochastic excitation technique applied to radio frequency spectroscopy such as ion cyclotron resonance and nuclear-magnetic resonance. The expressions reduce to particularly simple forms under two limiting cases. Under intermediate cases, numerical calculations have been performed for them. Their results and the inspection of the limiting forms confirm the following properties: (1) noise on the spectrum is mainly due to that employed for the excitation; (2) the signal-to-noise ratio is independent of the observation period and it is always unity; (3) resolution is given by the observation period and, in consequence, it increases linearly with the observation period. Finally, a comparison is made of some features for the present technique with three other techniques, namely, the pulsed Fourier transform, the rapid scan, and the conventional continuous-wave techniques. [ABSTRACT FROM AUTHOR]

We have applied the (Pb1-xLax)(ZryTiz)1-x/4 O3 (PLZT) electro-optic ceramic material to produce variable and rotatable waveplates for polarization controls. This plate has a 90 μm×90 μm window between four sides. Each of the four sides is coated with a material that acts as an electrode. The plate is inserted in a trench across an array of parallel optical waveguides. A single PLZT waveplate of this type was capable of continuous and complete conversion. This requires the control of only two parameters, the direction and strength of the applied voltage. The device is fast with a response time of only 1 μs [ABSTRACT FROM PUBLISHER]

In this letter, we report the single-mode operation of 1.55-μm buried heterostructure vertical-cavity surface-emitting lasers (VCSELs) fabricated on a GaAs-AlAs distributed Bragg reflector using thin-film wafer fusion. A 7-μm VCSEL exhibits a single transverse mode at up to about 0.1-mW maximum optical output power and 75°C maximum operation temperature under continuous-wave operation [ABSTRACT FROM PUBLISHER]

In this letter, we have developed thin liquid crystal (LC) arrays for use as simple polarization-controller arrays on planar lightwave circuits (PLCs). The 30-μm thick LC arrays are vertically inserted into trenches cut across PLC substrates. Two such LC cells that are in line and parallel to each other, one of which has a direction of alignment that is rotated by 45° relative to that of the other, are able to convert an arbitrary input polarization to a desired one. Twisted-nematic LC cells can switch the polarization of input light between the TE and TM modes with an extinction ratio of 15 dB [ABSTRACT FROM PUBLISHER]

We report a record low threshold current of 1.55-μm vertical-cavity surface-emitting laser (VCSEL). Thin-film wafer-fusion technology enables InP-based buried heterostructure VCSELs to be fabricated on GaAs-AlAs distributed Bragg reflectors. Threshold current density is independent of mesa size, and a 5-μm VCSEL exhibits a threshold current as low as 380 μA at 20°C and a single transverse mode up to the maximum optical output power under continuous-wave operation [ABSTRACT FROM PUBLISHER]

Variable optical attenuators using polymer-network liquid crystal have been integrated with the pitch of 250 μm on planar lightwave circuits. Trenches are cut in the direction perpendicular to the parallel light waveguides into planar lightwave circuits, a transparent electrode is deposited inside the trenches, and the trenches are filled with polymer-network liquid crystal. The typical attenuation range is 18 dB when the driving voltage is <20 Vrms at 1.55-μm wavelength. The power consumption is estimated to be very low (200 nW/ch) [ABSTRACT FROM PUBLISHER]

This paper describes compact variable optical attenuator arrays made by using fiber splicers and polymer-network liquid crystal. Fibers are inserted into the splicers and the gaps between the ends of the fibers are filled with the polymer-network liquid crystal. The residual loss for each array element is low (about 0.8 dB), the attenuation of 1.55-μm light is about 8 dB and the driving voltage is 20 Vrms . The polarization dependence is <2 dB. The power consumption is also very low (30 nW/ch). They are used for channel power equalizers for WDM systems [ABSTRACT FROM PUBLISHER]

The polarization stability of 850-nm InAlGaAs strained quantum-well (QW) vertical-cavity surface-emitting laser (VCSEL) grown on GaAs (311)B substrate was investigated by comparing it with that of GaAs unstrained QW VCSEL grown on GaAs (311)B substrate. Photoluminescence measurement showed that strained QWs grown on GaAs (311)B substrate had larger anisotropy in optical gain than unstrained QWs. The VCSEL with strained QWs showed an orthogonal polarization suppression ratio (OPSR) as high as 21 dB under CW operation. Time-dependent OPSR measurement indicated that the strained QW VCSEL had higher polarization stability than the unstrained QW VCSEL under zero-bias modulation [ABSTRACT FROM PUBLISHER]

All metal-organic chemical vapor deposition (MOCVD) grown 850-nm-wavelength refractive-index-guided semiconductor-buried vertical-cavity surface-emitting laser is proposed and their performance is investigated. P/n-InGaP current-blocking region enables both selective regrowth and the formation of refractive-index-guided region which surrounds multiquantum-well active/core regions. We have achieved room temperature CW operation of the new types of vertical-cavity surface-emitting lasers. The minimum threshold current was 9.5 mA with 18 μm square mesa size at 30°C. The device lased at up to 70°C, and the maximum output power exceeds 1 mW at above 30°C. The near field pattern indicates the single-lobed output beam at low bias current [ABSTRACT FROM PUBLISHER]

The polarization stability of 850-nm GaAs-based vertical-cavity surface-emitting lasers (VCSELs) under dynamic operation was investigated by comparing the characteristics of VCSELs grown on (311)B and (100) GaAs substrates. Significantly larger suppression ratios of the two orthogonal polarization modes was obtained for VCSELs on (311)B substrates than those on (100) substrates under zero-bias modulation. Time-dependent orthogonal polarization suppression ratio measurements also showed that the polarization direction was more stable in the VCSEL on (311)B substrates than that on (100) substrates. Error-free transmission was realized from VCSELs on (311)B substrates with and without a polarizer in both back-to-back and 100-m multimode fiber transmission [ABSTRACT FROM PUBLISHER]

High output power of about 800 mW in a chip and stable operation for over 14 000 h under 225 mW at 50°C have been achieved in 1.06 µm InGaAs strained-quantum-well laser diodes, which were realised by low-temperature growth of the InGaAs well layers. [ABSTRACT FROM AUTHOR]