Recent breakthroughs in photodetector and optical sensor technologies have increased the performance and functionality of a wide range of existing systems as well as enabling new applications. This talk will describe some of our work on a wide range of photodetectors. One recent project on ultraviolet photodiodes targets the development of smoke-detector-size sensors for hazardous biological agents that can be widely deployed in public facilities. Another research effort has incorporated new materials and impact ionization engineering with beneficially designed heterostructures and has achieved performance of avalanche photodiodes to levels previously thought to be theoretically unattainable. These photodiodes will be utilized in next-generation fiber optic systems that are projected to have transmission capacities as high as 10 terabits. In the infrared, quantum dot photodetectors that utilize nanostructures to confine carriers have recently achieved breakthrough detectivities and have the potential to achieve new levels of performance in infrared imaging with focal plane arrays.