Instructions: You are given a passage. You need to construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) its answer is the whole paragraph. Avoid creating questions that can be answered correctly without actually understanding the paragraph.
Input: A transistor laser is a solid-state device (i.e., fabricated in much the same way as computer chips) that emits coherent light--that is, light with essentially a single wavelength (a "pure" color) in which all of the wave crests are aligned.  This differs from light emitting diodes (LEDs), which are somewhat simpler solid-state devices that emit a range of wavelengths and do so in many directions at once.  Unlike traditional, bulky lasers, a transistor laser can be mass-manufactured very cheaply, and it can provide a natural bridge between electronic components and optical ones (e.g., fiber-optic networks).\n\nBecause the wave crests in laser light are all aligned, there is essentially no destructive interference between different light waves, so this form of light is very efficient in terms of power requirements and transmission distance.  That's why lasers are used in optical networking (especially telephony and long-haul Internet backbones) and also why it's dangerous to stare at one (the light energy is transferred to your retina so efficiently that it can destroy the cells).
Output:
what is a transistor laser?