High-power coherently coupled 8×8 vertical cavity surface emitting laser array

Abstract

We demonstrate record high pulsed output power exceeding 530 mW from an electrically pumped phase-coupled 8×8 vertical cavity surface emitting laser array (SELA) at room temperature. Three array types are compared: an 8×8 pixellated SELA(PSELA), an 8×8 grid contact SELA(CSELA), and a 78 μm×78 μm single broad area SEL(BSEL) emitter. The CSELA operating in a phase-coupled supermode exhibits the lowest threshold current (100 mA) and voltage (1.6 V), highest damage threshold and a smooth L-I characteristic with differential quantum efficiency ηd≳27%, the BSEL has the largest output power≳580 mW and a large ηd≳48%, the PSELA exhibited a large voltage with the largest ηd≳80%.

"Anti" up the aperture

“…Previous VCSEL array designs have attempted to select a single mode (i.e., all elements phase-locked) from the allowed bands of guided-modes of the 2-D photonic lattice. However, stable, high-power, diffraction-limited beam operation from 2-D VCSEL arrays has not been realized [21], [29], [30]. All previously reported phase-locked 2-D VCSEL arrays operate in either out-of-phase mode or a mixture of various modes, characteristic of weakly index-guided arrays, with poor intermodal discrimination.…”

“…These structures can be classified into either passive photonic lattices, with applications such as angular independent high-reflectivity mirrors [17] and low-loss defect-waveguides [18], or active photonic lattices, such as microcavity-defect lasers [19], 2-D distributed feedback-type lasers [20], 1-D antiguided phase-locked laser arrays [7], and 2-D VCSEL phase-locked arrays [21]. A common attribute shared by photonic-lattice-based devices, with the notable exception of antiguided-array structures [7], [8], [10], is that they are designed to operate within the photonic bands bounded by the light line (representing photon propagation in the low-index material) [16].…”

“…This terminology stems from the fact that the bands can be considered to originate from the guided modes of "high-index" waveguides, as shown schematically in Figure 3(a). For example, photonic-lattice structures such as coupled VCSEL arrays [21] confine light to the allowed optical modes within the guided-mode bands. Laser oscillation has also been reported from 2-D distributed feedback type structures constructed using organic or polymer gain materials [20] as well as semiconductor materials [23].…”

Two-dimensional phase-locked antiguided vertical-cavity surface-emitting laser arrays

“…However, stable, high-power, diffractionlimited beam operation from two-dimensional ͑2D͒ VCSEL arrays has not been realized. [1][2][3] In addition, all previously reported phase-locked 2D VCSEL arrays operate in either an out-of-phase mode or a mixture of various modes, characteristic of weakly index guided arrays, with poor intermodal discrimination. External phase shifters have also been used on optically pumped VCSEL arrays to obtain ''in-phase mode-like'' emission, 4 however the beam is quite broad.…”

Modal properties of two-dimensional antiguided vertical-cavity surface-emitting laser arrays

“…Previous VCSEL array designs have attempted to select a single-mode (i.e., all elements phase locked) from the allowed bands of guided-modes supported by the 2-D photonic lattice. The conventional approaches start with a large-area VCSEL structure, and incorporate a means to separate the individual array elements [3]- [6] such as: 1) pattern the array reflectivity so that the elements under the higher reflectivity regions have a lower threshold gain [3], [4]; 2) restrict the gain (injection current) to individual elements by selective ion implantation [5]; and 3) selectively etch the top surface so that the unetched regions form the higher-cavity-array elements [6]. These attempts to fabricate VCSEL arrays have successfully demonstrated phase locking among the array elements, emitting partially-coherent beams.…”