Maiman's doctoral thesis in experimental physics, under the direction of physicist Willis Lamb,[10] involved detailed microwave-optical measurements of fine structural splittings in excited helium atoms.

[22][23][24] On May 16, 1960, at Hughes' Malibu, California, laboratories, Maiman's solid-state pink ruby laser emitted mankind's first coherent light, with rays all the same wavelength and fully in phase.

[16] Maiman documented his invention in Nature[10][17][25] on August 6, 1960, after two rejections by Samuel A. Goudsmit at Physical Review Letters,[15] besides which he published other scholarly articles describing the science and technology underlying his laser.

[5]: 34–37 [29] Other major research groups at IBM, Bell Labs, MIT, Westinghouse, RCA and Columbia University, among others, were also pursuing projects to develop a laser.

His successful design used synthetic pink ruby crystal grown by the Linde Division of Union Carbide[15] as the active laser medium and a helical xenon flash lamp as the excitation source.

"[4]: 108  One piece of evidence that convinced Maiman (and later the world) that he had lased pink ruby was that "when the crystal was pushed above threshold, we observed a brightness ratio" of the twin red lines "of more than 50 times".

[15] Together they started a Verneuil plant to grow synthetic rubies, which were domestically available at that time only at Linde, who had been chosen by the US government to receive the WW2 technology transferred from Switzerland.

Brothers Rick and Tony Pastor were hired by Maiman from Hughes in order to start the Quantatron synthetic ruby plant.

[15] By 1962, when Smullin and Fiocco had already bounced the beam from a 50J 0.5 millisecond ruby laser off the moon, and the Soviets too,[33] Maiman had hired 35 people for his APL lab at Quantatron.

Maiman was awarded US Patent Number 3,353,115 for his "Ruby Laser Systems" on November 14, 1967, and paid $300 for it by assignee Hughes Aircraft Company.

[15] In 1971 Maiman founded the Laser Video Corporation, and from 1976 to 1983 he worked as vice president for advanced technology at TRW Electronics (now Northrop Grumman).

[36] In 1966 Maiman received the American Physical Society's Oliver E. Buckley Condensed Matter Prize and the Fannie and John Hertz Foundation Award for distinguished contribution in the field of science,[36] presented in a White House ceremony by President Lyndon B.

"[43] The annual Theodore Maiman Student Paper Competition was established in 2008, endowed by major laser groups, and is administered by the OSA Foundation.

[48] In 2014, the National Academy of Sciences published a biographical memoir of Maiman including a tribute by Nick Holonyak, Jr.[49] In 2017 UNESCO declared May 16 the International Day of Light, which is celebrated every year by numerous laser and light-related events around the world.

Maiman died from systemic mastocytosis on May 5, 2007, in Vancouver, British Columbia, Canada, where he lived with his second wife, Kathleen,[10][51] whom he met on February 13, 1984.