A wavelength-division-multiplexing (WDM) optical interconnect board providing broad-band transmission from a two-dimensional (2D) array of vertical-cavity surface-emitting lasers (VCSELs) to a 2D array of photodetectors is one of the attractive candidates for constructing future ultrahigh performance signal processing systems. Focusing grating couplers and distributed Bragg reflectors were integrated into a thin-film glass waveguide to form free-space-wave optical add/drop multi/demultiplexers required for the WDM optical interconnect board. A single-mode VCSEL was placed at the focal point of a focusing grating coupler, and a diverging wave from VCSEL was coupled and collimated into the waveguide. After 15 mm propagation, the guided wave was dropped by an optical drop demultiplexer to a focusing wave in free space. VCSEL was driven directly by a pulse pattern generator and the transmitted signal was detected. An open eye diagram of a 1 Gbps pseudo-random-binary-sequence non-return-to-zero signal was confirmed.

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Emission intensity patterns and spectra of a two-transverse-mode vertical-cavity surface-emitting laser (VCSEL) were observed and measured while the position and polarization of an optical feedback light were controlled. Lasing behavior was discussed in relation to linear polarization modes. The observed emission point shift with unchanged wavelengths was explained by the superposition of two newly appeared modes.