The laser was first built by the scientist Gordon Gould in 1958, but it was not until 1959 that the related paper was published, but it was rejected in the process of applying for a patent, because his tutor was Charles Townes, who was the inventor of maser (microwave resonator) technology (invented the technology of generating microwave output). Due to the influence of the tutor, the patent has not been approved. It was not until 1977 that the patent of laser was approved in the United States.
The long-term patent war is more beneficial to Gould, because when he obtained the patent, the laser had been widely used and was limited by the patent protection period. If the patent is approved as soon as it is applied, it won't make much money because it is not widely used.
Extended data:
Except for free electron lasers, the basic working principles of various lasers are the same. The necessary condition for generating laser is that the number of particles is reversed, and the gain is greater than the loss, so the necessary components of the device are excitation (or pumping) source and working medium with metastable energy level.
Excitation means that the working medium is excited to the excited state after absorbing external energy, which creates conditions for realizing and maintaining the inversion of particle number. There are light excitation, electric excitation, chemical excitation and nuclear energy excitation. The metastable energy level of the working medium makes stimulated radiation dominant, thus realizing optical amplification. A common component of a laser is a resonant cavity.
However, the resonator (see optical resonator) is not an indispensable part. The resonant cavity can make the photons in the cavity have the same frequency, phase and running direction, thus making the laser have good directivity and coherence. But also can shorten the length of the working substance, and adjust the mode of the generated laser by changing the length of the resonant cavity, so general lasers have resonant cavities.
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