M.L. Majewski

OPTICAL PROPERTIES OF METALLIC FILMS FOR VERTICAL-CAVITY OPTOELECTRONIC DEVICES

We present models for the optical functions of 11 metals used as mirrors and contacts in optoelectronic and optical devices: noble metals (Ag, Au, Cu), aluminum, beryllium, and transition metals (Cr, Ni, Pd, Pt, Ti, W). We used two simple phenomenological models, the Lorentz-Drude (LD) and the Brendel-Bormann (BB), to interpret both the free-electron and the interband parts of the dielectric response of metals in a wide spectral range from 0.1 to 6 eV. Our results show that the BB model was needed to describe appropriately the interband absorption in noble metals, while for Al, Be, and the transition metals both models exhibit good agreement with the experimental data. A comparison with measurements on surface normal structures confirmed that the reflectance and the phase change on reflection from semiconductor-metal interfaces (including the case of metallic multilayers) can be accurately described by use of the proposed models for the optical functions of metallic films and the matrix method for multilayer calculations.

Enhanced performance of offset-gain high-barrier vertical-cavity surface-emitting lasers

The temperature dependence and power output of vertical-cavity surface-emitting lasers (VCSELs) are addressed. The peak wavelength of the quantum well has been offset from the wavelength of the device cavity mode so that they are aligned at elevated temperatures. The result of this design change is to produce an 8- mu m-diameter VCSEL capable of operation to 145 degrees C, as well as CW operation of broad-area (70- mu m diameter) heat-sunk devices to record power levels. Fiber coupling experiments were also carried out, and a record 33-mW CW power was coupled to a multimode fiber. >

Modeling the optical dielectric function of GaAs and AlAs: extension of Adachi's model

Optical dielectric function model of Ozaki and Adachi [J. Appl. Phys. 78, 3380 (1995)] is augmented by introducing Gaussian‐like broadening function instead of Lorentzian broadening. In this way a consistent and comparatively simple analytic formula has been obtained, which accurately describes the optical dielectric function of GaAs and AlAs in a wide spectral range between 0.1 and 6 eV. The acceptance‐probability‐controlled simulated annealing technique was used to fit the model to experimental data.

Design of microchannel free-space optical interconnects based on vertical-cavity surface-emitting laser arrays

We investigate the design of free-space optical interconnects (FSOIs) based on arrays of vertical-cavity surface-emitting lasers (VCSELs), microlenses, and photodetectors. We explain the effect of the modal structure of a multimode VCSEL beam on the performance of a FSOI with microchannel architecture. A Gaussian-beam diffraction model is used in combination with the experimentally obtained spectrally resolved VCSEL beam profiles to determine the optical channel crosstalk and the signal-to-noise ratio (SNR) in the system. The dependence of the SNR on the feature parameters of a FSOI is investigated. We found that the presence of higher-order modes reduces the SNR and the maximum feasible interconnect distance. We also found that the positioning of a VCSEL array relative to the transmitter microlens has a significant impact on the SNR and the maximum feasible interconnect distance. Our analysis shows that the departure from the traditional confocal system yields several advantages including the extended interconnect distance and/or improved SNR. The results show that FSOIs based on multimode VCSELs can be efficiently utilized in both chip-level and board-level interconnects.

Analysis of lensless free-space optical interconnects based on multi-transverse mode vertical-cavity-surface-emitting lasers

The feasibility of lensless free-space optical interconnects (FSOIs) using Vertical-Cavity-Surface-Emitting Lasers (VCSELs) is investigated. The signal-to-noise ratio (SNR) and interconnect capacity of FSOIs in the presence of higher order modes are analyzed. The dependence of the SNR on feature parameters of VCSEL and photodetector arrays and the dependence of the capacity on channel spacing are simulated. The results have shown that lensless FSOIs can be achieved in chip level applications and the presence of higher order modes will deteriorate their performance. Moreover, the maximum distance of interconnection and the effect of lateral misalignment are also investigated.

Method for characterization of intrinsic and extrinsic components of semiconductor laser diode circuit model

A simple method for the characterization of the intrinsic and extrinsic parameters of a semiconductor laser diode has been described. This method is based on the measurement of intensity noise, small-signal modulation response and input reflection coefficient of the device. The intrinsic 3-dB-modulation bandwidth and the extrinsic parasitic components associated with the device can be readily determined by using the analytical expressions presented. It has been shown that the major limitation of the 3-dB-modulation bandwidth can be attributed to the device chip RC time constant.<<ETX>>

Direct intensity modulation in sampled-grating DBR lasers

In this letter, we present new experimental results obtained for direct intensity modulation of widely tunable sampled-grating distributed Bragg-reflector (SGDBR) lasers. These results are of significance to SGDBR applications in wavelength-division-multiplexing systems. The devices described operate in the C-band (wavelength range 1525-1565 nm). A 6-GHz small-signal modulation bandwidth and >10-dB signal extinction ratio under large-signal operation were obtained. We have also recorded an undistorted eye pattern for a nonreturn-to-zero random signal 2/sup 31/-1 word length at 2.5-Gb/s bit rate during transmission over 75-km of standard single-mode fiber.

Relative intensity noise measurements of a widely tunable sampled-grating DBR laser

The intensity noise of a sampled-grating distributed Bragg reflector laser with 50-nm tuning range and 45-dB side-mode suppression ratio has been measured. The resonance frequency, damping factor, and modified Schawlow-Townes linewidth are extracted from the noise spectra. At high output power, the relative intensity noise (RIN) of the laser is below the photodiode shot noise limit, which is -160 dB/Hz. The laser has uniform shot noise limited RIN properties along the whole tuning range. The maximum resonance frequency is 5.4 GHz at a bias current of 120 mA and the K factor is 0.58 ns.

Modeling the optical constants of AlxGa1−xAs alloys

The extension of Adachis model with a Gaussian-like broadening function, in place of Lorentzian, is used to model the optical dielectric function of the alloy AlxGa1-xAs. Gaussian-like broadening is accomplished by replacing the damping constant in the Lorentzian line shape with a frequency dependent expression. In this way, the comparative simplicity of the analytic formulas of the model is preserved, while the accuracy becomes comparable to that of more intricate models, and/or models with significantly more parameters. The employed model accurately describes the optical dielectric function in the spectral range from 1.5 to 6.0 eV within the entire alloy composition range. The relative rms error obtained for the refractive index is below 2.2% for all compositions

A Critical Comparison of High-Speed VCSEL Characterization Techniques

This paper critically compares, for the first time, common microwave and optical procedures used for the high-speed characterization of vertical-cavity surface-emitting lasers (VCSELs). The intrinsic small-signal modulation characteristics of a VCSEL are measured, and the related rate equation parameters are extracted. Observed trends show excellent agreement with theory. The modulation characteristics of the VCSEL are determined by examining three different responses: relative intensity noise, S21 response, and high-resolution optical spectra. The various experimental techniques yielded consistent results. The relative strengths and weaknesses of each measurement are investigated