Laser and Photonics Reviews Vol.7 Nr.6, 1027 - 1035 ; An integrated photonic-on-a-chip device based on a single organic-inorganic di-ureasil hybrid was fabricated for optical waveguide and temperature sensing. The device is composed by a thermal actuated Mach-Zehnder (MZ) interferometer operating with a switching power of 0.011 W and a maximum temperature difference between branches of 0.89 oC. The MZ interferometer is covered by a Eu3+/Tb3+ co-doped di-ureasil luminescent molecular thermometer with a temperature uncertainty of 0.1oC and a spatial resolution of 13 µm. This is an uncommon example in which the same material (an organic-inorganic hybrid) that is used to fabricate a particular device (a thermal-actuated MZ interferometer) is also used to measure one of the device intrinsic properties (the operating temperature). The photonic-on-a-chip example discussed here can be applied to sense temperature gradients with high resolution (10-3 oC·µm-1) in chip-scale heat engines or refrigerators, magnetic nanocontacts and energy-harvesting machines. An integrated photonic-on-a-chip device based on a single organic-inorganic di-ureasil hybrid was fabricated for optical waveguide and temperature sensing. The device is composed by a thermal actuated Mach-Zehnder (MZ) interferometer operating with a switching power of 0.011 W and a maximum temperature difference between branches of 0.89 oC. The MZ interferometer is covered by a Eu3+/Tb3+ co-doped di-ureasil luminescent molecular thermometer with a temperature uncertainty of 0.1oC and a spatial resolution of 13 µm. This is an uncommon example in which the same material (an organic-inorganic hybrid) that is used to fabricate a particular device (a thermal-actuated MZ interferometer) is also used to measure one of the device intrinsic properties (the operating temperature). The photonic-on-a-chip example discussed here can be applied to sense temperature gradients with high resolution (10-3 oC·µm-1) in chip-scale heat engines or refrigerators, magnetic nanocontacts and energy-harvesting machines.