a photodetecting section that detects the laser light that has passed through the cell wherein the cell has at least a laser light reflection section inside thereof application_number US 71466810 A description preferred embodiments of the invention are described below with reference to the accompanying drawings fig1 is a perspective view of the structure of an atomic frequency acquisition apparatus 100 in accordance with an embodiment 1 of the invention fig2 a is a cross sectional view taken along a line a a u2032 in fig1 and fig2 b is an upper plan view of the atomic frequency acquisition apparatus 100 the atomic frequency acquisition apparatus 100 may be used to acquire a time standard frequency in a cpt type atomic clock as shown in fig1 and fig2 a and 2b the atomic frequency acquisition apparatus 100 is equipped with a cell 110 a laser diode i e a laser light source 120 and a photodetector photodetection section 130 which are mounted on a substrate 200 of an electronic apparatus having an electronic clock mounted therein a heater 300 is mounted on an upper surface of the cell 110 the laser diode 120 the photodetector 130 and the heater 300 are connected to a driver circuit by wirings not shown the cell 110 is disposed on the substrate 200 with protruded sections 114 the laser diode 120 and the photodetector 130 are formed in one piece in accordance with.