Abstract
We report on near infrared semiconductor nanopatch lasers with subwavelength-scale physical dimensions (0.019 cubic wavelengths) and effective mode volumes (0.0017 cubic wavelengths). We observe lasing in the two most fundamental optical modes which resemble oscillating electrical and magnetic dipoles. The ultra-small laser volume is achieved with the presence of nanoscale metal patches which suppress electromagnetic radiation into free-space and convert a leaky cavity into a highly-confined subwavelength optical resonator. Such ultra-small lasers with metallodielectric cavities will enable broad applications in data storage, biological sensing, and on-chip optical communication.
Highlights
Coherent light sources with subwavelength length scales are of considerable interest in view of their applications in optical interconnects [1, 2], data storage [3], biological/chemical sensing [4], and imaging [5]
The refractive index of TiO2 was set to 2.4. This value is uncertain and depends on the atomic layer deposition quality, the sensitivity of TiO2 index variation is minimal since most of the electromagnetic field is confined to the semiconductor region
We have fabricated and characterized subwavelength-scale nanopatch semiconductor lasers at near infrared wavelengths. Both the effective mode volume and physical size of the nanopatch lasers are kept at subwavelength-scales because of tight optical confinement from metallodielectric resonators
Summary
Coherent light sources with subwavelength length scales are of considerable interest in view of their applications in optical interconnects [1, 2], data storage [3], biological/chemical sensing [4], and imaging [5]. Semiconductor lasers with subwavelength volume are interesting because their sizes start to approach those of transistors in silicon integrated circuits. Several novel semiconductor laser structures have been experimentally demonstrated to reduce laser sizes, including photonic crystals [6,7,8], microdisks [9], metalclad cavities [10,11], nanowires [5, 12, 13], and hybrid metal-nanowire waveguides [14]. Focus has only been put on reducing physical laser sizes in only one or two dimensions, such subwavelength lasers may find their greatest applications when they are physically small. Reducing the third dimension remains the most difficult challenge as radiation and/or ohmic losses increase rapidly. Noginov et al reported a deepsubwavelength laser based on modified Cornell dots [15]; the use of dye molecules as the gain material precludes electrical pumping or high-speed modulation
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