DoE researchers have developed a bright terahertz laser:

T-rays still constitute a gap in the science of light and energy. They inhabit a region of the electromagnetic spectrum remaining to be better understood—and much better exploited. Now that a way to generate them at high power has been demonstrated, T-rays can potentially extend and add widely to the wave-based technologies that have defined the last century and a half, from the telegraph, radio and X-rays to computers, cell phones and medical MRIs.

I had an opportunity to tour the Advanced Light Source. The professor who was showing us around took great care not to call this a "laser". First, the mechanism by which the light is generated is different. Light is generated by perturbing the path of a packet (one of a train of packets pushed and maintained through the ring) of fast moving electrons (synchotron radiation) as opposed to the simultaneous emission of light by excited atoms or molecules in a resonance chamber. Genuine lasers (at least in visible and longer wavelength) tend to be more coherent and have a narrower frequency range than the corresponding synchotron derived light sources above.

As I understand it, the three key properties of a system like the one described in the above article is the speed of the electron packets, how much current (ie, charge per second) passes through whatever strong magnetic fields bend these electron packets (combination of packet size, spacing of the packets, and packet speed), and finally how much energy gets extracted out of an electron packet when it is induced to emit light. The speed determines the frequency and the latter two determine how bright the source is. What sounds like has happened here is that the researchers in the story made some significant breakthroughs on increasing the size of the packets.

In any case, according to this Nature article, they (the scientists in Rand's story) generated a 20W beam at around 0.6 THz, but they originally had generated a beam with 550 times that power (their instruments couldn't operate in that range). A 10kW beam is rather impressive.