TECHNICAL FIELD

This disclosure relates generally to photonic integrated circuit (PIC) technologies and more particularly to planar lightwave circuits (PLCs) exhibiting controllable transmissivity/reflectivity.

BACKGROUND

As is known, PLCs have found widespread applicability in a number of technological arts including communications and biomedical instrumentation—among others. In a number of such applications, controlling light that propagates through the PLC (i.e., transmissivity/reflectivity of the PLC) is of critical importance. Given this importance, systems, methods structures that provide or otherwise facilitate control of the transmissivity/reflectivity of a PLC would represent a welcome addition to the art.

SUMMARY

An advance in the art is made according to aspects of the present disclosure which describes systems, methods and structures that include a resonant mirror assembly having a number of cascaded resonators that provide or otherwise facilitate the control of the transmissivity/reflectivity of a planar lightwave circuit (PLC)—or portion thereof—over a range of 0% to substantially 100%.

Viewed from a first aspect, the present disclosure describes a planar lightwave circuit comprising an input port; an output port; and a resonant mirror assembly optically coupling the input port to the output port, the resonant mirror assembly including a number of cascaded optical resonators, each optical resonator exhibiting a pair of coupling coefficients, wherein one of the coupling coefficients of at least one of the plurality of resonators is different in value from all the other coupling coefficients. Of particular advantage, such difference may be achieved at the time of fabrication and/or during operation of the PLC.

Viewed from another generalized aspect the present disclosure is directed to a planar lightwave circuit comprising an input waveguide; an output waveguide; n optical resonators where n>=3; n+1 bus waveguides, each of bus waveguides having a first end and a second end; a first coupler optically coupling the input waveguide to the first end of the first one of the n bus waveguides and to the first end of the nth of the n bus waveguides; a second coupler optically coupling the output waveguide to the second end of the first one of the n bus waveguides and to the second end of another one of the n bus waveguides; wherein each of the n optical resonators are optically coupled to at least two of the bus waveguides, each of the resonator bus couplings being defined by a coefficient K; and wherein at least one of the coefficients is different in value from all of the others.

Viewed from still another generalized aspect of the present disclosure is directed to a lightwave circuit—i.e., lasers—including an energy source—i.e., a pump or pump source—a gain medium or laser medium, and mirrors that form an optical resonator wherein a plurality of the optical resonators are configured in parallel and share a common resonant mirror assembly positioned at one (i.e., distal) end of the optical resonators. In sharp contrast to the prior art, such multiple-gain lasers according to the present disclosure allows for higher output power than the prior art. In further contrast to the prior art, systems, and structures according to the present disclosure allow for the construction of tunable, narrow linewidth, laser. By increasing the number of gain sections—according to aspects of the present disclosure—a laser having increased output power while maintaining tunability and narrow linewidth. According to aspects of the present disclosure, such is obtained advantageously—and surprisingly—through the use of a single, common, frequency selective mirror that is shared and used by all the gain sections in the structure. In this inventive manner, the gain sections are combined in parallel into a single, overall laser structure.

As we shall show and describe and as will be readily appreciated by those skilled in the art, by increasing the number of gain sections in parallel and sharing a mirror assembly, the more gain sections added the more power may be produced. Using the same mirror for each cavity allows for extremely low linewidths with high output power while still exhibiting tunability.

