Cascaded-mode resonators

A device, comprising:

• a mirror and a mode converter that define a region between the mirror and the mode converter, the region configured to contain a plurality of orthogonal modes of a wave;
• wherein the wave, when sent from outside the region and when propagating from the mirror towards the mode converter, comprises a first mode of the plurality of orthogonal modes;
• wherein the mode converter is configured to convert the wave from the first mode of the plurality of orthogonal modes, to a second mode of the plurality of orthogonal modes that is different from the first mode;
• wherein the mirror is configured to reflect the wave with the second mode of the plurality of orthogonal modes towards the mode converter;
• wherein the mode converter is configured to convert the wave from the second mode of the plurality of orthogonal modes to the first mode of the plurality of orthogonal modes;
• and
• wherein the mirror is configured to reflect the wave with the first mode of the plurality of orthogonal modes towards the mode converter.

A device, comprising:

• a first mode converter and a second mode converter that define a region between the first mode converter and the second mode converter, the region configured to contain a plurality of orthogonal modes of a wave;
• a first free-space input channel coupled with the first mode converter;
• and
• a second free-space input channel coupled with the second mode converter;
• wherein the wave, when sent from outside the region and when propagating from the first mode converter towards the second mode converter, comprises a first mode of the plurality of orthogonal modes;
• wherein the second mode converter is configured to convert the wave from the first mode of the plurality of orthogonal modes, to a second mode of the plurality of orthogonal modes that is different from the first mode;
• and
• wherein the first mode converter is configured to convert the wave to the first mode of the plurality of orthogonal modes.