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Photonics
Published in Ajawad I. Haija, M. Z. Numan, W. Larry Freeman, Concise Optics, 2018
Ajawad I. Haija, M. Z. Numan, W. Larry Freeman
For example, consider a crystal of aluminum oxide (Al2O3) in which some of the Al3+ ions are replaced with Cr3+. This is called a ruby and is usually identified by its red color. This represents a material that has an available metastable state. A light pump excites more than half of the chromium ions to the excited state of about 2.25 eV, and they spontaneously decay to the metastable state at about 1.79 eV. The excess energy is absorbed by the other ions in the lattice, causing the stimulated emission of radiation of wavelength of approximately 694 nm to the rapid transition from the metastable state to the ground state. The ruby rod is precisely made to have a length that is an integer multiple of a half wavelength in order to produce resonant standing waves. One end is mirrored and the other end partially mirrored to allow some of the light to exit the end. It is surrounded by a xenon flash tube used as the light pump. There is a pulse of 694 nm red light emitted from the partially mirrored end of the ruby for every flash of the light pump. The ruby laser was the first laser ever fabricated by Theodore H. Maiman (1927–2007) at Hughes Research Laboratories in 1960. Charles H. Townes (1915–2015), Alexander M. Prokhorov (1916–2002), and Nikolay G. Basov (1922–2001) were awarded the Nobel Prize in 1964 for their pioneering work that made the laser possible.
Lasers
Published in Abdul Al-Azzawi, Photonics, 2017
As shown in Figure 31.14, the atoms are excited from state E1 to state E3. This process is called optical pumping. The atoms quickly decay either back to E1 or to the intermediate state E2, which is metastable with a lifetime of about 3×10−3 s (compared to 10−8 s for ordinary levels). With strong pumping, more atoms can be forced into the E2 state than are in the E1 state. Thus, we have the inverted population needed for lasing. As soon as a few atoms in the E2 state jump down to E1, they emit photons that produce stimulated emission of the other atoms, and the lasing action begins. A Ruby laser thus emits a beam whose photons have 1.8 eV of energy and a wavelength of 694.3 nm (ruby-red light).
Laser Technology
Published in Abdul Al-Azzawi, Fibre Optics, 2017
Figure 11.14 shows energy level diagram for ruby laser. The atoms are excited from state E1 to state E3. This process is called optical pumping. The atoms quickly decay either back to E1 or to the intermediate state E2, which is metastable with a lifetime of about 3 × 10−3 second (compared to 10−8 second for ordinary levels). With strong pumping, more atoms can be forced into the E2 state than are in the E1 state. Thus we have the inverted population needed for lasing. As soon as a few atoms in the E2 state jump down to E1, they emit photons that produce stimulated emission of the other atoms and the lasing action begins. A ruby laser thus emits a beam whose photons have 1.8 eV of energy and a wavelength of 694.3 nm (ruby-red light).
Use of lasers in minimally invasive spine surgery
Published in Expert Review of Medical Devices, 2018
In 1917, Albert Einstein established the theoretical background of the laser, the ‘stimulated emission.’ In the 1950s, Charles Hard Townes, Nikolay Basov, and Aleksandr Prokhorov independently worked on the ‘maser’ (microwave amplification by stimulated emission of radiation) technology. They shared the Nobel Prize in Physics in 1964. In 1959, the term ‘laser’ was first published in literature by Gordon Gould [15,16]. On 16 May 1960, Theodore H. Maiman [17] showed the first functioning laser at Hughes Research Laboratories in Malibu, California. The laser consisted of a ruby laser stimulated by a flash bulb and emitted light in the red spectral range of 694 nm [18].