Distributed feedback lasers produced using soft lithography

Research in microfabrication is important to many areas of science and technology. An emerging set of microlithographic techniques, known as soft lithography, uses elastomeric elements for microcontact printing (μCP), molding, or near field photolithography. We describe the use of two soft lithographic techniques to build DFB lasers with narrow emission linewidths. This demonstrates the suitability of soft lithography for building structures that have (i) feature sizes (∼300 nm) significantly less than 1 μm, and (ii) long-range (∼1 mm) spatial coherence. The lasers use optically pumped gain material deposited on a DFB resonator formed from periodic relief on the surface of a transparent substrate. The required relief was generated on glass and polymer surfaces with μCP and replica molding respectively. μCP produced lines of gold on a glass slide; RIE using the gold as a resist generated periodic relief (600 nm period, 50 nm depth) on the glass surface. Polymer gratings with similar dimensions were formed by curing a polyurethane film against an elastomeric mold. The good performance of the lasers suggest the potential utility of soft lithographic techniques for low-cost fabrication of high-performance optoelectronic devices. Other types of resonators, including distributed Bragg reflector and quasi two-dimensional photonic bandgap based resonators can also be fabricated with the techniques demonstrated here.