[[quoteright:320:[[Series/StarTrekVoyager http://static.tvtropes.org/pmwiki/pub/images/StarTrekBrig.jpeg]]]]
[[caption-width-right:320:Keep it down in there! We barely have enough budget to reuse old SpecialEffects!]]

->''"I just wanna get it on record that using force fields for doors in a space prison... is a bad idea. You know what would have been better? Regular doors, with locks! Locks that don't open when the POWER goes out!"''
-->-- '''[[AlternateUniverse Space Warden!]]Cave Johnson''', ''VideoGame/{{Portal 2}}''

A standard way to bar entry or exit for characters in SpeculativeFiction is to use a Force Field Door. It may be made of SomeKindOfForceField, glowing bars of PureEnergy, [[GeometricMagic concentric]] InstantRunes, or what have you. If touched, it may harmlessly shock or ''dematerialize'' the appendage doing the touching. Sometimes, especially if the field is invisible until touched, it leads to amusing situations where characters run face first into the field.

Aside from RuleOfCool, the advantage of such a setup is usually that it is immune to physical attack, or that it can contain StarfishAliens that could [[IntangibleMan phase]] or [[ShapeShifting shape-shift]] their way through ordinary doors.

Of course, the flaw in this immaterial marvel is it usually requires an outside energy source, or can be interfered with by using powerful ECM or MCM[[note]][[AntiMagic Magic Counter Measures)]][[/note]]. So the hero can traipse past these obstacles by pulling the proverbial plug on it. Worse is when the outside energy source is on the ''outside'' of the Force Field Door, making disabling it as easy as beating up some guards and blowing it up[[note]](Which may actually be a challenge if guarded by EliteMooks or the like)[[/note]]. Or blowing a hole in the wall on the side, whichever is easiest. For some reason, the jailers rarely use physical doors outside the field (or wrapped in the field) as a backup in case of power failure.

If the force field door is on every side of a room, then it's like a ForceFieldCage, which redirects to this trope.

[[TropeCo/ForceFieldDoor This item]] is available for purchase thanks to TropeCoŽ.
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!!Examples:

[[foldercontrol]]

[[folder:Films -- Animated]]
* ''WesternAnimation/MonstersVsAliens'': Gallaxhar puts Ginormica in a force field cage... which she then tears apart ''with her bare hands!'' Makes sense, as she is full of {{Unobtainium}}, which is more powerful than anything Gallaxhar has.
* ''WesternAnimation/TitanAE:'' Cale is thrown into one of these energy jails by the [[AliensAreBastards Dredj]]. Seemingly inescapable, his only hope is to [[spoiler:touch the walls, using his fingers force himself out of the cell]].
* Likewise, the cell blocks in ''Anime/FinalFantasyTheSpiritsWithin''. So naturally, when the city's power grid goes down, so do the "bars" in the cells.
[[/folder]]

[[folder:Films -- Live-Action]]
* ''Nightlife'', a 1980s vampire TV movie starring Mirriam D'abo and Ben Cross, featured a doctor jury rigging a prison cell for a vampire by hanging ultraviolet lamps above the only doorway into a room, as well as on the ceiling a few feet down the hall in either direction. If the vampire crossed the beam, he burst into flames. See it [[http://www.youtube.com/watch?v=uzwD3uLGbwg#t=0m25s here]].
* ''Franchise/StarWars'' had several, most notably the barrier that forces ObiWan and Darth Maul to wait momentarily before their battle.
** Just about every large starship in ''Star Wars'' has some part of the hull, usually a hangar, that's open to the vacuum of space. How do crew members breath and not get sucked out into the void? Force fields.
** And they do apparently have physical doors as a backup: a Trade Federation battleship gets its shield generators blown up, and immediately closes physical doors over the hangar. The hangers are kept open normally so that in an emergency the starfighter squadrons can be launched at a moment's notice rather than having to wait for the doors to open.
* The cell doors in ''Film/{{Tron}}'' are beams of energy. Admittedly, they are already in the internet and ''everything'' is energy, but there are still solid objects.
* In ''Film/StarTrekGenerations'', Soran protected his missile launch site with a massive force field wall. Unfortunately, it didn't penetrate the ground, which allowed Picard to bypass it through a tight rock arch it happened to rest on. Also an inversion, as Soran is the one inside the force field.
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[[folder:Literature]]
* Creator/RobertAHeinlein's ''HaveSpaceSuitWillTravel''. When Kip and Peewee are on the planet Lanador they find a PeopleZoo with several persons held behind force field doors.
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[[folder:Live-Action TV]]
* In ''Series/StargateAtlantis'' the titular city had holding cells with energy shields covering actual bars. The [[NeglectfulPrecursors Ancients]] weren't ''that'' self-confident.
** Whoever designed the brig must have suffered from some kind of acute practicality syndrome, because the Ancients ''really are'' that self-confident. Case in point, a force field is the only thing holding the ''air inside Atlantis'' when it's in space.
** Atlantis also has one built into its Stargate, serving [[PortalSlam the same function]] as the Iris on Earth's Stargate, with the extra advantage that it can't be overheated by firing exotic weapons through the Stargate (something Earth's Iris has had to deal with).
* ''Series/StargateSG1'' once featured an interesting variant -- a prison cell that used the ''force of gravity'' as its "Force-Field Door". The cell was a long corridor with a dead end hooked up to an ArtificialGravity generator. When this was turned on, the end of the corridor became the floor of a deep pit, thus preventing escape for anyone inside (and ensuring a painful landing for an unprepared prisoner). When turned off, the "pit" became a corridor again, and guards could walk in or out. The resulting perspective shifts allowed for nice little CameraTricks. The flaw was the same as that of any Force-Field Door: [[NoGravityForYou cut the power]], and the prisoner can simply walk out.
** They should have built the cell as a pit, and used the artificial gravity generator to get in and out. ... Or a ladder.
* One ''Series/StarTrekTheNextGeneration'' episode "We'll Always Have Paris" had the bar variant in Dr. Manheim's lab.
** Cell doors in ''Series/StarTrekTheNextGeneration'' and ''[[Series/StarTrekDeepSpaceNine Deep Space Nine]]'' were energy fields.
*** [[ShapeShifter Odo]] from ''[[Series/StarTrekDeepSpaceNine Deep Space Nine]]'' had to be held in a room surrounded entirely with force fields, to keep him from escaping in his liquid form.
** Add ''Series/StarTrekTheOriginalSeries'', e.g. "Assignment Earth".
** ''Series/StarTrekVoyager'' (in general a frequent offender with this trope) actually had an episode in which ''Voyager'' was temporarily converted into a PrisonShip, transporting a large number of dangerous alien prisoners in a converted cargo bay. Of course, all the cells added to the bay had Force-Field Doors. Predictably, a StandardStarshipScuffle ensued, and, lo and behold, the very first victim of SubsystemDamage was the cargo bay's power... The OhCrap expressions on the bridge crew's faces when they learned of this were priceless. "Oh, woe, if only there was some other way we could have locked up those prisoners!"
** ''Series/StarTrekEnterprise'', being set in the [[TheVerse 'verse's]] past, was the exception and had a good old-fashioned solid door for their brig, made out of some reinforced transparent material. It seemed to work just as well as the force-field doors on all the later ''Enterprises''...
* In the ''Series/{{Firefly}}'' episode The Train Job, in the intro, Mal is thrown through what is evidently a force-field window: it vanishes as he passes through it, before reappearing a moment later. Assuming it performs the actual function of a window (keeping outside air out, and inside air in), it's most certainly an example of this trope, but they're never seen again.
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[[folder:Tabletop Games]]
* ''TabletopGame/DungeonsAndDragons'' adventure S3 ''Expedition to the Barrier Peaks''. The spaceship's police headquarters had cells with 3 normal walls and one force field wall.
** D&D in general likes its magical force wall/cage effects. Depending on the edition, though, this can be justified in that those don't actually depend on an external power source and can be effectively indestructible if the exact right countermeasures aren't at hand, making permanent versions potentially actually superior to mundane physical barriers.
[[/folder]]

[[folder:Videogames]]
* These appear in ''VideoGame/BatmanArkhamAsylum''. They must be turned off before Bats can go further.
* These show up occasionally in the ''Franchise/CrashBandicoot'' series of games. Typically in the Warp Rooms, barring off access to later chambers until you clear the one before it.
* In ''VideoGame/HalfLife2'' some of the obstacles included energy fields to which you needed to shut off the power to get past. Often by literally pulling out a (inexplicably large) wall plug.
** These fields also allow combine troops (and trains) though while preventing Gordon and his rebel friends access.
* In ''Franchise/{{Metroid}}'' games, doors are, [[VideoGame/MetroidOtherM with one exception,]] surrounded by force fields. These are always ColorCodedForYourConvenience and thus a BrokenBridge till you collect the right upgrade.
** The Prime series actually justifies the door-shields: the door were set up to separate distinct areas from each other. The doors are actually motion-activated, opening when a sufficiently large life-form approaches it, but to prevent the doors opening and closing ceaselessly for the indigenous life, the force-field was set up, which could only be deactivated by an energy weapon from a sufficiently advanced species. It wasn't so much to keep people in and out of certain areas (though that's inevitably what they do...to Samus), but rather to ''[[MundaneUtility prevent wear and tear]]'' from constantly opening and closing.
* In ''KnightsOfTheOldRepublic 2'', the Exile, Atton, and Kreia find themselves in force cages repeatedly, which Atton [[LampshadeHanging lampshades]].
** Both games feature quite a few force field cages and doors. Some of these require you have certain members in your party before you can pass through them (e.g Jolee to get down to the Lower Shadowlands on Kashyyyk).
* In ''RaidouKuzunohaVsKingAbaddon'' [[spoiler:Dahn and his rogue Fukoshi]] are imprisoned in one. The "forcefield" can't be seen through, but the unoccupied cells in the same room have backup bars. (The forcefield is in place to block [[spoiler:their insect summoning whistles]].)
* In ''[[VideoGame/DarkForcesSaga Jedi Knight: Jedi Academy]]'', one mission involves escaping from a prison where an enemy has thrown Jayden. Each prison cell has four walls but no doors. The ceiling is a force field. Smart design, considering most people can't jump that high. Not smart when you put a Jedi (who can jump that high) in one of these cells and then ''[[WhatAnIdiot let him out]]'' to play [[HuntingTheMostDangerousGame the most dangerous game]] [[SuicidalOverconfidence with him]].
* Common in the ''Franchise/RatchetAndClank'' series. Sometimes Ratchet (or Clank) has to step on a button to open them, sometimes he has to trick or persuade some other character to step on the button, and sometimes he has to destroy the mechanism.
* The ''VideoGame/{{Fallout}}'' series has [[http://fallout.wikia.com/wiki/Repulsion_device multiple]] kinds of forcefields.
* Shows up a lot in the modern SonicTheHedgehog games. They usually require you to flip a switch or destroy an encounter's worth of enemies to drop them. Other puzzles revolve around activating these to use as a walkway and sometimes even navigating mazes made entirely of them.
* In ''VideoGame/SuperheroLeagueOfHoboken'', Dr Entropy protects his first dastardly device behind a force field... but while the generator is placed on the inside, its power cord is plugged into an outlet on the outside, allowing the heroes to disable the field with one swift pull.
* In the Perpetual Testing Initiative for ''VideoGame/{{Portal 2}}'', an alternate Cave Johnson learns the hard way why these things are bad idea on a PrisonShip--especially when you consider power outages.
-->'''Cave''': Man, those blue force fields looked good, though. Every time I saw one, I thought, "Wow! I am in space." Still, though...A door made out of paper would have been better in the long run. Would have at least slowed 'em down for a second.
* VideoGame/UnrealI has them all over, as well the consequences of turning off the power...
* VideoGame/{{Warframe}} features these heavily on both [[MegaCorp Corpus]] and [[TheEmpire Grineer]] ships. The former will deplete your shields, and fling you away from the door, as if you were struck by a shockwave, and need to be disabled by shooting (or staying out of sight of) security cameras, and the latter will proc Magnetic damage on you, draining all of your shields ''and'' energy, and are disabled by shooting ID scanner over the doorframe.
* ''VideoGame/{{Dishonored}}'' has force fields (called Walls of Light) that zap to ash anyone/thing unauthorized that tries to go through them. There are plenty of ways to circumvent them, however; there's usually an alternate entrance, you can remove the power source, you can rewire them to let ''you'' through and obliterate guards, and you can just throw stuff through the field until it runs out of power. One particular odd form of the latter is summoning a swarm of rats and guiding them into the wall. Two expensive ways to get through them involve DemonicPossession of a guard who ''is'' authorized and hop across that way, and the other is to use the advanced version of Bend Time to literally stop time and cross without fear of being zapped.
* In ''Videogame/{{Arcanum}}'', [[spoiler: Arronax]] was captured by BigBad and kept in a magical force field capsule barely lagrer than his body for [[AndIMustScream two thousand years]].
[[/folder]]

[[folder:Webcomics]]
* ''QuentynQuinnSpaceRanger'' (an InSpace! spinoff from ''TalesOfTheQuestor''): during an arc skewering ''Franchise/StarTrek'', the main character is placed in a cell guarded by a force field and discovers he's been furnished with a replicator that can produce any food or drink he wishes. He fabricates a glass of water and [[NoWaterProofingInTheFuture shorts out]] the door. [[http://www.rhjunior.com/QQSR/00030.html You can see it here]].
* In ''Webcomic/ElGoonishShive'', Raven considers it "[[http://www.egscomics.com/?date=2009-06-06 standard lockdown procedure]]" to put up force fields sealing off all the doors and some of the hallways when his school is under a magical threat. Not that it stops Abraham however.
[[/folder]]

[[folder:Web Originals]]
* The ''Website/CollegeHumor: Troopers'' episode [[http://www.collegehumor.com/video/6439036/troopers-forcefield "Forcefield"]]
[[/folder]]

[[folder:Western Animation]]
* The supervillain prisons in AvengersEarthsMightiestHeroes used this kind of door.
[[/folder]]

[[folder:Real Life]]
* [[http://en.wikipedia.org/wiki/Plasma_window Plasma window]]. No, really.
* Considering that atoms are mostly empty space, and only feel solid due to the strong negative charge present on their surface (such that it is) which repels other atoms in a similar manner to what happens when you try to touch the south poles of two magnets together, ordinary doors are technically examples of this trope.
[[/folder]]

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