Directed energy weapons (DEWs) use highly focused energy to create
destructive effects across the electromagnetic spectrum
— radio waves, visible light, or infrared heat. DEWs that could produce effects similar
to an EMP are of particular concern for electric grid security,
because they do not involve the complexity of a missile launch and nuclear
detonation. Additionally, DEWs allow an adversary to target specific facilities rather
than a wide swath of territory, making their use a far less escalatory option.
While many DEWs are in the development stages and many details remain classified,
other nations, particularly China, have placed an emphasis on their development and
fielding.
Similar to EMP, mitigating a potential DEW strike involves a combination of
hardening key nodes and improving grid response and resiliency.

Source: page 19 at http://www.thepresidency.org/sites/default/files/pdf/Grid%20Report%20July%2015%20First%20Edition.pdf