Transverse mode discrimination in long-wavelength wafer-fused vertical-cavity surface-emitting lasers by intra-cavity patterning.

Transverse mode discrimination is demonstrated in long-wavelength wafer-fused vertical-cavity surface-emitting lasers using ring-shaped air gap patterns at the fused interface between the cavity and the top distributed Bragg reflector. A significant number of devices with varying pattern dimensions was investigated by on-wafer mapping, allowing in particular the identification of a design that reproducibly increases the maximal single-mode emitted power by about 30 %. Numerical simulations support these observations and allow specifying optimized ring dimensions for which higher-order transverse modes are localized out of the optical aperture. These simulations predict further enhancement of the single-mode properties of the devices with negligible penalty on threshold current and emitted power.

Intra-cavity patterning for mode control in 1.3 µm coupled VCSEL arrays.

We report coupled VCSEL arrays, emitting at 1.3 µm wavelength, in which both the optical gain/loss and refractive index distributions were defined on different vertical layers. The arrays were electrically pumped through a patterned tunnel junction, whereas the array pixels were realized by intra-cavity patterning using sub-wavelength air gaps. Stable oscillations in coupled modes were evidenced for 2x2 array structures, from threshold current up to thermal roll-over, using spectrally resolved field pattern analysis.

1.3 microm-wavelength phase-locked VCSEL arrays incorporating patterned tunnel junction.

We report the fabrication and the performance of phase-locked VCSEL arrays emitting near 1310 nm wavelength. The arrays were fabricated using double wafer fusion by patterning a tunnel junction layer, which serves to define the individual single mode array elements. Phase-locking in both one-dimensional and two-dimensional array configurations was confirmed by means of far field and spectral measurements as well as theoretical modeling. CW output powers of more than 12 mW were achieved.

Electro-optic and nonlinear optical properties of ion implanted waveguides in organic crystals.

We report on the electro-optic and nonlinear optical properties of waveguides produced by low fluence (Phi = 1.25x10(14) ions/cm(2)) H+ ion implantation in the organic nonlinear optic crystal 4-N,N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST). The profile of the nonlinear optical susceptibility has been determined by measuring the reflected second-harmonic generation efficiency from a wedged-polished sample at a fundamental wavelength of lambda(omega) = 1176nm. In the waveguide core region the nonlinear optical susceptibility is shown to be preserved to more than 90% of its bulk value. A model which relates the molecular changes to the measured macroscopic alteration of the refractive index and the nonlinear coefficient has been introduced to quantify the fraction of molecules modified by ion implantation. Furthermore, a first electro-optic modulation in ion implanted DAST waveguides has been demonstrated.

Ion implanted optical waveguides in nonlinear optical organic crystal.

We report for the first time to our knowledge optical waveguiding in an organic crystalline waveguide produced by ion implantation. Using H+ ions a refractive index barrier suitable for waveguiding has been realized in the highly nonlinear optical organic crystal 4-N, N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST). The refractive index changes in the waveguiding region as a function of the distance from the surface have been measured. Maximal refractive index changes of up to -0.2 and -0.1 at wavelengths of 633nm and 810nm have been realized, respectively. The waveguide refractive index profiles as a function of the ion fluence have been determined. Planar waveguiding has been demonstrated by polishing sharp edges and using conventional end-fire coupling. The measured losses are approximately 7 dB/cm at 1.57mum.

Direct electron beam writing of channel waveguides in nonlinear optical organic crystals.

We report on optical channel waveguiding in an organic crystalline waveguide produced by direct electron beam patterning. The refractive index profile as a function of the applied electron fluence has been determined by a reflection scan method in the nonlinear optical organic crystal 4-N, N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST). A maximal refractive index reduction of Deltan1 = -0.3 at a probing wave-length of 633 nm has been measured for an electron fluence of 2.6mC/cm(2). Furthermore, a new concept of direct channel waveguide patterning in bulk crystals is presented and waveguiding has been demonstrated in the produced structures by end-fire coupling. Mach-Zehnder modulators have been successfully realized and a first electro-optic modulation at a wavelength of lambda= 1.55mum has been demonstrated therein.