Laser beam power measurement

Claim 3

A method of measuring a beam power according to claim 1, wherein the second step is done with a photoelectric detector after the lifetime of a singlet excited state has passed after the irradiation, and the third step comprises amplifying the output photo-current of said detector, taking the square root thereof, and the inverse square root, holding up the inverse of the square root for a certain time on one hand, differentiating the inverse of the square root on the other hand, multiplying both of these values and the inverse of the product of the lifetime of a singlet state of the crystal, the duration of irradiation, coefficient of photon absorption for the transition to said singlet excited state, and the triplet-triplet annihilation rate constant, and taking the square root of their product to obtain the beam power.

Claim 4

A beam power meter comprising: a body of a molecular crystal for receiving and transmitting a laser beam to be measured, the molecular crystal being capable of emitting fluorescence of the first and secondary process; a photoelectric detector means for detecting the intensity of the fluorescence from said body after the lifetime of the singlet excitation state has passed from the time of the emission of fluorescence; amplifier means for amplifying the photo-current F from said detector means; a first circuit means including a differentiation circuit for shaping the photo-current into a pulse, a delay circuit for giving a delay to the pulse signal, and a gate circuit for receiving the delayed pulse signal; a second circuit means including a gate circuit for receiving the photo-current F, a delay circuit for receiving said shaped pulse signal and sending it to the gate circuit with a delay to open the gate, a function generator for taking the square root of the photo-current Square Root F, and an inverse number generator for taking the inverse of the square root of the photo-current 1/ Square Root F (t) and sending it to both the gate circuit of saId first circuit means and a differentiation circuit; a hold-up circuit for receiving the initial value of 1/ Square Root F through the gate circuit of the first circuit means upon releasing of the gate; multiplier circuit means for receiving 1/ Square Root F t from the hold-up circuit and from the differentiation circuit of said second circuit means calculating and a function generator connected to the multiplier circuit for taking the square root of the input to obtain the beam power of the laser beam to be measured; gamma being the triplet-triplet annihilation rate constant, KST being the rate constant of radiationless singlet-triplet conversion from the excited state 1B2u to the excited state 3B2u, tf being the lifetime of the excited state 1B2u, t11 being the duration of irradiation of the laser beam under measurement, and delta being the coefficient of two photon absorption.

Claim 5

A beam power meter comprising: a body of a molecular crystal for receiving and transmitting a laser beam to be measured, the molecular crystal being capable of emitting fluorescence of the first and secondary process; a photoelectric detector means for detecting the intensity of the fluorescence from said body after the lifetime of the singlet excitation state has passed from the time of the emission of fluorescence; amplifier means for amplifying the photo-current F from said detector means; a first circuit means including a differentiation circuit for shaping the photo-current into a pulse, a delay circuit for giving a delay to the pulse signal, and a gate circuit for receiving the delayed pulse signal; a second circuit means including a gate circuit for receiving the photo-current F, a delay circuit for receiving said shaped pulse signal and sending it to the gate circuit with a delay to open the gate, a function generator for taking the square root of the photo-current Square Root F, and an inverse number generator for taking the inverse of the square root of the photo-current 1/ Square Root F (t) and sending it to both the gate circuit of saId first circuit means and a differentiation circuit; a hold-up circuit for receiving the initial value of 1/ Square Root F through the gate circuit of the first circuit means upon releasing of the gate; multiplier circuit means for receiving 1/ Square Root F t from the hold-up circuit and from the differentiation circuit of said second circuit means calculating and a function generator connected to the multiplier circuit for taking the square root of the input to obtain the beam power of the laser beam to be measured; gamma being the triplet-triplet annihilation rate constant, KST being the rate constant of radiationless singlet-triplet conversion from the excited state 1B2u to the excited state 3B2u, tf being the lifetime of the excited state 1B2u, t11 being the duration of irradiation of the laser beam under measurement, and delta being the coefficient of two photon absorption.

Claim 6

A beam power meter according to claim 3, wherein said molecular crystal is selected from the group consisting of anthracene, pyrene, phenanthrene, and 3,4-benzpyrene.