Very-small-aperture Laser Research Articles

Sub-wavelength beam lasers with surface plasmon structures

The simulation of a plasmonic very-small-aperture laser is demonstrated in this paper. It is an integration of the surface plasmon structure and very-small-aperture laser (VSAL). The numerical results demonstrate that the transmission field can be confined to a spot with subwavelength width in the far field (3.5 μm far from the emitting surface), and the output power density can be enhanced over 30 times of the normal VSAL. Such a device can be useful in the application of a high resolution far-field scanning optical microscope.

Matching the emitting wavelength from a very-small-aperture laser to the resonant property of a nanometric C-aperture

An experimental method is proposed to increase the output power from a C-aperture very-small-aperture laser (VSAL). This method is based on the resonant property of a C aperture and the tunability of the emitting wavelength from a VSAL. The drive current of the VSAL is altered to tune the emitting wavelength. The experimental results indicate that, when the emitting wavelength matches the resonant wavelength of the C aperture fabricated on the VSAL, the output power is enhanced 7.2 times. So a strong output power from a C-aperture VSAL can be obtained with small power consumption. This study may be useful to the design and application of a VSAL.

Experimental investigation on the oscillation of very-small-aperture lasers with different depth grooves on their front facets

Surface corrugations are commonly used to increase the output power from a very-small-aperture laser (VSAL) by exciting surface plasmons. Some experimental results indicate that a VSAL cannot be lased if surface corrugations are fabricated, whereas some experimental results indicate that it can be lased. In order to investigate the oscillation condition, we fabricated VSALs with a finite array of grooves. Different depth grooves are fabricated by controlling the focused ion-beam etching time. The experimental results demonstrate that the threshold current of a VSAL increases when the grooves are deepened. At the same time, the slope efficiency decreases, and the laser linewidth increases. The physical mechanism behind these experimental results is discussed. The experimental results imply that there is a critical groove depth. The grooves should be shallower than this critical value in order to obtain a laser oscillation and the surface plasmon enhancement effect. An enhancement factor of 2.4 is finally obtained when the VSAL is lased properly. These experimental results may be revelatory for the design and optimization of a VSAL.

Experimental investigation of the performance of an annular aperture and a circular aperture on the same very-small-aperture laser facet

A very-small-aperture laser (VSAL) with a circular aperture has a trade-off between the spot size and the output power. A nanometric annular aperture is fabricated to overcome this difficulty. The advantages of the annular aperture are demonstrated by measuring and comparing its near-field intensity distribution with that of a circular aperture. These apertures are fabricated on the same VSAL to ensure that they are under the same illumination conditions. The experimental results indicate that an annular aperture produces a smaller spot size and a higher peak intensity than a circular aperture. The confinement effect and the enhancement effect are attributed to the convergence of the power flow that passes through the annular aperture. The observed enhancement effect decreases when the distance from the VSAL facet is increased, but it does not vanish even when the distance is as large as 3.5 microm.

Experimental Investigation of an L-Shaped Very-Small-ApertureLaser

An L-shaped very-small-aperture laser (VSAL) with high power output andfield enhancement effect is fabricated and characterized. As acomparison, a conventional rectangular VSAL and a double-aperture VSALcontaining one L-aperture and one rectangular aperture are alsofabricated and measured. The confined optical fields in the vicinity ofapertures of VSAL are detected using an apertured near-field scanningoptical microscope. The experimental results reveal that the poweroutput from the L-shaped VSAL increases about 13 times than therectangular VSAL with a comparable aperture area. It is indicated thatthe L-shaped VSAL has strong power output enhancement effect. Thenear-field distribution of the double-aperture VSAL indicates that theL-aperture has the field confinement and enhancement effect strongerthan the rectangular aperture.

Near-field scanning optical microscopy with an active probe

A near-field scanning optical microscopy (NSOM) system employing a very-small-aperture laser (VSAL) as an active probe is reported in this Letter. The VSAL in our experiment has an aperture size of 300nm×300nm and a near-field spot size of about 600nm. The resolution of the NSOM system with the VSAL can reach about 600nm, and even 400nm. Considering the high output power of the VSAL, such a NSOM system is a potentially useful tool for nanodetection, data storage, nanolithography, and nanobiology.

Aperture shape effect on the performance of very small aperture lasers

We report on the effect of different aperture shapes on the power output of a very small aperture laser (VSAL) fabricated from commercial edge-emitting laser diodes and correlate the results to the layer structure and polarization of the optical field. A waveguide theory is used to explain the experimental observations. We show that the shape of the aperture has a significant effect on the VSAL output power. In particular shapes exploiting the asymmetry of the laser can achieve much higher throughput over square apertures while keeping the aperture area constant. This work also indicates the validity of analyzing near-field small apertures as cutoff waveguide structures.

High-power laser light source for near-field optics and its application to high-density optical data storage

A laser light source for high-resolution near-field optics applications with an output power exceeding 1 mW (104 times the power from previous sources) and small (300 nm square to less than 50 nm square) output beam size is demonstrated. The very-small-aperture laser (VSAL) tremendously expands the range of applications possible with near-field optics and increases the signal-to-noise ratios and data rates obtained in existing applications. As an example, 250-nm-diam marks corresponding to 7.5 Gb/in.2 storage density have been recorded and read back in reflection and transmission on a rewritable phase-change disk at 24 Mb/s with a 250-nm-square aperture VSAL. VSALs potentially enable data storage densities of over 500 Gb/in.2 (up to 100 times today’s magnetic or optical storage densities).