Home Optics Experiments PE-1500 Ruby Excited Lifetime & Spectroscopy


  • Ruby Crystal
  • Absorption Spectrum
  • Emission Spectrum
  • Lifetime of excited state
  • Einstein Coefficient for Spontaneous Emission
  • Blue LED
  • Spectrometer
  • Spontaneous Emission
  • Stimulated Emission


Basic experiment

Intended institutions and users:

Physics Laboratory

Engineering department

Electronic department

Biophotonics department

Physics education in Medicine



How it works ...


PE-1500 Ruby Excited Lifetime & Spectroscopy

The invention of the Ruby Laser by Theodore Mayman in 1960 initiated the era of photonics technologies. This exciting experiment steps into the footmarks tracks of famous scientists and provides a comprehensive inside of fundamental quantum optics. Although the Ruby Laser did not find great application it is still the first Laser system which is introduced to students as first invented Laser. By means of a couple of simple components great physics can be demonstrated. Due to the broad absorption bands of the Ruby crystal peaking around 405 nm as well as 560 nm either blue or green emitting LED or laser diodes can be used as excitation source. However, here a blue LED is used which emits less than 5 mW at a wavelength of 460 nm.

PE-1500 Ruby Excited Lifetime & Spectroscopy

The light of the DPSSL (Diode Pumped Solid State Laser) is focused by the Lens L1 into the synthetic Ruby crystal ball. The created fluorescence is focused by the lens L2 to the photodiode PD. The filter FI blocks the pump radiation. The modulator switches the DPSSL periodically on and off. A reference signal of the modulator is connected to the channel 2 of an oscilloscope. The amplified fluorescence signal is connected to the channel 1 of the oscilloscope. The trigger is set to the modulation signal channel. The decay time of the fluorescence signal is in the range of milliseconds so that a simple oscilloscope can be used to measure the lifetime of the excited state. Instead of the photodiode the fibre of the provided spectrometer is used, allowing the recording of the fluorescence spectrum.

PE-1500 Ruby Excited Lifetime & Spectroscopy

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