Is the exact same laser used to read both Blu-ray and 4k discs?

[mdhaus]

I tried searching for this and got some conflicting information.

Do 4K UHD players use the exact same "blue" laser to read both 4K discs and Blu-ray discs? Even though the data on 4K discs is much more compacted, does the player use the same laser it uses for Blu-ray discs? Or are there two "blue" lasers in the player - one for standard Blu-ray discs and another for the much more dense 4K discs?

I know they carry a "red" laser for DVDs and CDs...but I wasn't sure if anything extra was needed for the "step-up" to 4K playback from regular Blu-ray playback.