No, putting two light-emitting diodes (LEDs) together does not create a laser beam with a longer wavelength. LEDs and lasers are fundamentally different in how they produce light.
An LED emits incoherent light, which means the emitted photons have different phases and do not have a well-defined direction. Each LED emits light independently, and their emitted light does not have the necessary properties for constructive interference to occur and create a laser beam.
On the other hand, a laser is a device that produces coherent light through a process called stimulated emission. It amplifies light by bouncing photons back and forth between mirrors, causing the emitted photons to have the same wavelength, phase, and direction. The resulting light is highly monochromatic, coherent, and tightly focused.
To create a laser beam of a specific wavelength, you need a laser diode designed to emit light at that specific wavelength. Laser diodes are engineered with specific materials and structures to achieve population inversion and stimulate emission of coherent photons.
While it is possible to combine multiple laser beams of different wavelengths using beam-combining techniques, simply putting two LEDs together does not create a laser beam or change the wavelength of the emitted light. Each LED would continue to emit light independently, and the resulting light would not have the characteristics of a laser beam.
In summary, combining LEDs does not produce a laser beam with a longer wavelength. LEDs emit incoherent light, while lasers produce coherent light through stimulated emission, requiring specialized laser diodes designed for specific wavelengths.