Did Luke Skywalker use the Dark Side against Vader in Episode VI (Return of the Jedi)?

Question

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@1:00 Vader refers to Leia saying “perhaps she will [turn to the dark side]” enraging Luke, who screams “nooooo” and goes on the offensive (also looks like Luke switched to Djem So?)

@2:00 Sidious says “your hate has made you powerful,” as if to confirm Luke did indeed use the dark side for that moment.

Besides speculation on my part, is there any out-of-movie confirmation that Luke did indeed (or didn’t) use the dark side for that moment?

Note: The closest related question I found was: Did Luke Skywalker go to the Dark Side? which looks to be its own independent question.

Answer 1

Yes.

one of the Rebel Star Cruisers that was surging in the midst of the heaviest fighting. And in the next instant, the Star Cruiser was vaporized. Blown to dust. Returned to its most elemental particles, in a single burst of light.

In the numbing grip of despair, with the hollowest of voids devouring his heart, Luke’s eyes, alone, glinted—for he saw, again, his lightsaber, lying unattended on the throne. And in this bleak and livid moment, the dark side was much with him.

(ROTJ novelization by James Kahn)

and then, when defeating Vader:

“Never!” he screamed. His lightsaber flew off Vader’s belt into his own hand, igniting as it came to him.

He rushed to his father with a frenzy he’d never known. Nor had Vader.
...
Blow upon blow, Luke forced Vader to retreat—back, onto the bridge that crossed the vast, seemingly bottomless shaft to the power core. Each stroke of Luke’s saber pummeled Vader, like accusations, like screams, like shards of hate.

...

Luke stared at his father’s twitching, severed, mechanical hand—and then at his own black-gloved artificial part—and realized suddenly just how much he’d become like his father. Like the man he hated.

Trembling, he stood above Vader, the point of his glowing blade at the Dark Lord’s throat. He wanted to destroy this thing of Darkness, this thing that was once his father, this thing that was … him.

Suddenly the Emperor was there, looking on, chuckling with uncontrollable, pleased agitation. “Good! Kill him! Your hate has made you powerful! Now, fulfill your destiny and take your father’s place at my side!”

Luke stared at his father beneath him, then at the Emperor, then back at Vader. This was Darkness—and it was the Darkness he hated. Not his father, not even the Emperor. But the Darkness in them. In them, and in himself.

Answer 2

Absolutely

The Disney canon novelization Beware the Power of the Dark Side! makes this very clear. Not only is Luke using the dark side when he defeats Vader, he’s employing it throughout the scenes in the throne room.

To start with, the Emperor is described as "bringing out Luke’s own dark side."

“Your friends up there on the forest moon are walking into a trap. As is your rebel fleet! It was I who allowed the Alliance to know the location of the shield generator. It is quite safe from your pitiful little band. An entire legion of my best troops awaits them.”

Now the fear in Luke’s heart grows—they are doomed! And the fear quickly turns to anger. He whirls back to face the Emperor but his gaze lands on his weapon. Oh, how quickly the Emperor has brought out Luke’s own dark side! And now to push him just a little further….

_{Beware the Power of the Dark Side!}

Luke is explicitly described as employing the dark side against Vader. Indeed, he only is winning because of the dark side:

He falls and Luke is preparing to leap down after him when he hears the Emperor behind him.

“Good. Use your aggressive feelings, boy. Let the hate flow through you.” Again, the Emperor is telling the truth and Luke knows it. He has won, but only by using the dark side of the Force. The hate is flowing through him and he is winning this battle against his father because of it.

_{Beware the Power of the Dark Side!}

Later, when Vader taunts Luke about Leia turning to the dark side:

“Sister! So…you have a twin sister. Obi-Wan was wise to hide her from me. But now his failure is complete. Your feelings have betrayed her, too. If you will not turn to the dark side, perhaps she will.”

“Never!” screams Luke, launching himself out of the gloom, lightsaber blazing, fighting as he has never fought before. He swings wildly, madly, using the dark side to move faster and strike harder. He has felt anger and hate before, but never this much fear…fear for his sister, Leia.

_{Beware the Power of the Dark Side!}

Of the Sith trinity (anger, fear, and hatred) Luke is particularly employing fear here.

So Luke definitely employs the dark side. It’s part of his temptation by the Emperor. But, unlike his father, Luke rejects this power: As George Lucas says:

So that isn’t what the Emperor had in mind. He wanted this really super guy, but that got derailed by Obi-Wan. So he finds that, with Luke, he can get a more primo version if he can turn Luke to the Dark Side. You’ll see, as this goes on, Luke is faced with the same issues and practically the same scenes that Anakin is faced with. Anakin says yes and Luke says no.