By the two-dimensional triangular holey structure, a high-power stable single-mode operation was demonstrated in oxide confined 850nm vertical-cavity surface-emitting lasers. For two types of hole alignments, the lasing operation was observed with different near field patterns, i.e., a single spot pattern and a floral pattern. The former showed an output power of 2mW with a high side-mode suppression ratio (SMSR) of 45–50dB, which is explained by the selective loss mechanism. The latter showed a high power of 7mW with a SMSR of 40dB. The observed lasing spectrum and far field pattern indicate that it is a deformed fundamental mode whose bright spots extending over the device are in-phase oscillating. This device structure will be effective for the enhancement of single-mode power in devices with any material system.

We demonstrate nonvolatile two-color holographic recording in as-grown and reduced Er-doped LiNbO3. It is found that, unlike the case of near-stoichiometric LiNbO3 reported previously, the diffraction efficiency can be increased by a factor of ∼ 5 after the reduction treatment. The recording sensitivity and the figure of merit M/# for the reduced crystal are measured to be 9×10-4 cm/J and 0.02, respectively, with a 488-nm gating beam at an intensity of 1 W/cm2 and 780-nm writing beams at a total intensity of 2 W/cm2. Results of the light-induced absorption measurement suggest that the small polarons are responsible for the two-color photosensitivity in Er-doped LiNbO3.

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The two-color recording sensitivity S and the figure of merit M/# are measured in a reduced and congruent LiNbO(3):In crystal of 2.2-mm thickness. The results are compared with those before reduction treatment. It is found that S increases by an order of magnitude through reduction treatment but the M/# is unchanged. Measured values for S and M/# in the reduced crystal are found to be 3 x 10(-3) cm/J and 0.04, respectively, with a total writing intensity of 4.0 W/cm(2) at 780 nm and a gating intensity of 1.15 W/cm(2) at 488 nm. These values are close to those of near-stoichiometric LiNbO(3) crystals under similar recording conditions. We also show that photoconductivity plays an important role in the improvement of S in LiNbO(3):In.