An on-chip technique for noncontact electrical testing of a test structure on a chip is provided. On-chip photodiodes receives pump light from a pump light source, where the on-chip photodiodes are electrically connected to the test structure and are configured to generate power for the test structure. An on-chip coupling unit receives probe light from a probe light source, where the on-chip coupling unit is optically connected to on-chip waveguides through which the probe light is transferred. On-chip switches open in response to receiving voltage output from the test structure, and the on-chip switches remain closed when the voltage output is not received from the test structure. The on-chip switches pass the probe light when opened by the voltage output from the test structure. The on-chip switches block the probe light by remaining closed, when the voltage output is not received from the test structure.