Thin Film Optical Frequency Doubler Using a Grating Coupler
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
The surface or local electric field associated with a surface plasmon polarition (SPP) can be enhanced by a factor of 50-100 over the incident or exciting field by employing a grating coupler that can couple nearly all (approximately 99%) of the energy from a coherent source into the SPP which propagates at a metal/insulator interface. Since the cross section for harmonic generation varies as the 4th power of the field, the SPP may be used to enhance the efficiency of frequency doubling by (50)(4) - (100)(4) or up to a factor of 10 for a given non-linear material. An appropriate corrugated grating structure is shown in the figure. The optimum grating amplitude for efficient coupling depends on dielectric losses in the metal and insulator. Silver gives low losses at optical frequencies.