Ling Bao

Near-diffraction-limited coherent emission from large aperture antiguided vertical-cavity surface-emitting laser arrays

We demonstrate that in-phase mode operation with a near-diffraction-limited beam can be realized in large aperture (up to 100 elements) antiguided vertical-cavity surface-emitting laser (VCSEL) arrays. A selective etching process with two-step metalorganic chemical vapor deposition is used for fabrication of the antiguided VCSEL array structures. Modal discrimination is enhanced by intentionally choosing a GaAs cap thickness so as to introduce suitable loss to array interelement regions. Far field patterns indicate in-phase mode operation from both triangular and rectangular geometry antiguided VCSEL arrays, which is in good agreement with theory.

Modeling, fabrication, and characterization of large aperture two-dimensional antiguided vertical-cavity surface-emitting laser arrays

We have investigated the modal behavior of two-dimensional (up to 400 elements) active-photonic-lattice-based antiguided vertical-cavity surface-emitting laser (VCSEL) arrays by both modeling and device characterization. A two-dimensional (2-D) model based on the effective index method has been constructed to analyze 2-D resonance and calculate array mode frequencies in rectangular geometry arrays. A more comprehensive three-dimensional bi-directional beam propagation code has also been developed to theoretically describe 2-D antiguided arrays with the VCSEL structure in the primary wave propagation direction. Gain spatial hole burning (GSHB) effects above laser threshold are applied to find conditions favorable for in-phase mode lasing and high intermodal discrimination. Three rectangular geometry array structures based on different interelement loss mechanisms have been designed and fabricated. Both far-field and spectral characterization were conducted on the devices to make detailed comparison with theoretical results. We found that introducing higher loss within the interelement region can allow the in-phase mode to exhibit the lowest threshold gain for a wide range of interelement widths around the in-phase resonance condition. A detailed spectral study of 5/spl times/5 arrays with the highest interelement loss design has demonstrated suppression of competing guided array modes and higher order leaky array modes at drive currents up to 10 times threshold.

Antiresonant reflecting optical waveguide-type vertical-cavity surface emitting lasers: comparison of full-vector finite-difference time-domain and 3-D bidirectional beam propagation methods

The cold-cavity modal characteristics of an antiresonant optical waveguide-type cylindrical vertical-cavity surface-emitting laser (VCSEL) are investigated through numerical simulations using a three-dimensional (3-D) bidirectional beam propagation method (BD-BPM) and a full-vector axisymmetric finite-difference time-domain (FDTD) method. Good agreement between the BPM- and FDTD-computed radial mode profiles as well as the mode-dependent radiation losses is obtained. The results of this paper establish the accuracy of the BD-BPM technique for simulating this class of devices and confirm effective-index method predictions that antiresonance conditions for cylindrical geometry devices (i.e., VCSELs) differ from those of planar geometry devices (i.e., edge emitters).

Leaky defect modes of two-dimensional VCSEL arrays

Two-dimensional photonic lattices with a low-index defect have been studied. Simulations demonstrate that this type of structure has potential for realizing single-spatial mode operation from a relatively large emitting aperture, making it ideal for fiber coupling applications. A 2-D finite difference model is used to calculate the radiation loss of the modes in various low-index defect based two-dimensional photonic lattices. The simulation results are also compared to the results from a comprehensive the 3-D bi-directional beam propagation model. These calculations have been used to guide mask design and the experimental realization of the defect VCSEL devices.

Coherent emission from large aperture antiguided vertical cavity surface emitting laser arrays

The in-phase mode emission in coupled VCSELs and 2D 4/spl times/4 VCSEL arrays has been reported using antiguided VCSEL elements. Two-step metalorganic chemical vapor deposition (MOCVD) is used for the growth of the antiguided VCSEL array structure. Here we demonstrate that in-phase mode operation can be achieved from very large aperture (up to 20/spl times/20) rectangular and triangular antiguided VCSEL arrays in good agreement with theory. Simulation studies give insight into the mode discrimination mechanisms in these structures. A 3D biidirectional beam propagation method is also used to study both cold cavity and above threshold properties in our large aperture antiguided VCSEL arrays.

Modeling and observations of modal structure in antiguided VCSEL array

Modal behavior of a 2-D (square lattice geometry) antiguided vertical cavity surface emitting laser (VCSEL) array was studied by 3-D bi-directional beam propagation method. Above threshold operation of leaky modes was simulated using multiple iterations. Besides, a method based on functions of Krylov’s subspace, was developed to find a number of array optical modes in a VCSEL array with gain and index distributions established by the oscillating mode. In calculations, both Fourier and space variable descriptions of beam propagation were combined. The FFT technique was used for calculations of the Fourier image and the original. Conditions are found for favorable lasing of the in-phase mode providing high laser beam quality. Experimentally realized 5x5 laser array was studied numerically. The 2-D antiguided array results from shifting the cavity resonance between the element and inter-element regions and is fabricated by selective chemical etching and two-step metalorganic chemical vapor deposition (MOCVD) growth. In-phase and out-of-phase array mode operation is observed from top-emitting rectangular arrays as large as 400 elements, depending on the inter-element width, in good agreement with theory.

Modal properties of 2D anti-guided vertical cavity surface emitting laser arrays

The paper focuses on the detailed modal property analysis of anti-guided VCSEL arrays and the application of an analytical approximation to explain the experimental spectral data.

Modal characteristics of large-aperture ARROW VCSELs

Antiresonant reflecting optical waveguide (ARROW) vertical cavity surface emitting lasers (VCSELs) are designed for high power single mode operation. Scalar wave and finite-difference time domain (FDTD) studies indicate large modal discrimination in favor of the fundamental mode for large aperture (8 um) ARROW VCSELs. The modal discrimination mechanisms are identified through the total modal loss and quality factor calculations including polarization dependence. A novel design is presented, utilizing metal absorption loss to help suppress higher-order modes.