Square-lattice photonic band-gap single-cell laser operating in the lowest-order whispering gallery mode

Abstract

Square-lattice photonic band-gap lasers are realized at room temperature from single-cell photonic crystal slab microcavities fabricated in InGaAsP quantum-well materials emitting at 1.5 μm. This single-cell photonic band-gap laser operates in a class of two-dimensional mode to be classified as the smallest possible whispering gallery mode with genuine energy null at the center. The low-loss nondegenerate mode with modal volume of 0.1 (λ/2)3 demonstrates a spectrometer-limited below-threshold quality factor >2000 and a theoretical quality factor >10 000. The other class of photonic crystal lasers is also observed outside the photonic band gap of the square lattice, operating in the dipole mode.

Optimization of the Q factor in photonic crystal microcavities

“…The imperfect confinement in the third dimension produces some unwanted out-of-plane loss (radiation loss), which is usually a limiting factor in the performance of these structures. The problem of the factor optimization in planar photonic crystal microcavities has been addressed recently by several groups [2], [14]- [17]. The cavities that we proposed have a potential for achieving together with the mode volume of the order of one half of the cubic wavelength of light in the material [2], [16].…”

The smallest possible whispering-gallery-like mode in the square lattice photonic-crystal slab single-defect cavity

“…There are two types of resonant modes in this cavity, as mentioned in our previous work [15]. One has a fourfold symmetry and is nondegenerate.…”

“…A single-defect cavity formed in a free-standing photonic-crystal slab supports the resonant mode whose volume is only a few times [13], [15]. The 's of the single-defect cavity mode are reasonably large and show lasing action [13]- [15]. Therefore, very high Purcell enhancement is achievable in the photonic-crystal slab single-defect cavity by combining the small-mode volume with a high-quality factor of the mode.…”

“…Very recently, authors have reported lasing action from the square-lattice photonic-crystal single-defect cavity freestanding in air [15]. This square-lattice single-defect laser operates in a new type of 2-D resonant mode to be classified as the smallest possible whispering gallery mode.…”

“…A relatively simple way to achieve strong 3-D photon confinement is to combine a two-dimensional (2-D) photonic crystal with a strong-guiding slab waveguide [5], [12]. A single-defect cavity formed in a free-standing photonic-crystal slab supports the resonant mode whose volume is only a few times [13], [15]. The 's of the single-defect cavity mode are reasonably large and show lasing action [13]- [15].…”