Henry Spencer wrote:

The idea is not ridiculous, but advanced propulsion in general is very
poorly funded. The laser rocket suffers from needing a very large laser,
which is a big up-front capital expense.

Yes. The rule of thumb is that a laser to launch 1kg payload to orbit
needs 1 MW. Another rule of thumb is that currently lasers cost order
$1/watt and are getting rapidly cheaper.

However a laser rocket might currently make more sense as a second
stage- the power of the laser is proportional to the thrust required and
the thrust required goes down with burn time, and after staging; this
means that less than the 1MW rule of thumb is needed.

In addition, fuel for laser rockets is very lightweight (pun not
intended, often hydrogen is proposed), and so the first stage would
benefit from not having to carry so much mass.

For near-term applications, it
is not obvious that the money needed for that wouldn't be better spent on
improved application of conventional rocket technology.

Possibly- but it's not completely clear. In particular laser launch
usually deals with smaller orbital payload sizes than conventional
rocketry sensibly can address. Whether there is a market for small
payloads isn't all that clear however.