How to open popup in Lightning Component?

You can create modal provided by Salesforce

<div class="demo-only" style="height: 640px;">
<section role="dialog" tabindex="-1" aria-labelledby="modal-heading-01" aria-modal="true" aria-describedby="modal-content-id-1" class="slds-modal slds-fade-in-open">
<div class="slds-modal__container">
<header class="slds-modal__header">
<button class="slds-button slds-button_icon slds-modal__close slds-button_icon-inverse" title="Close">
<svg class="slds-button__icon slds-button__icon_large" aria-hidden="true">
<use xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="/assets/icons/utility-sprite/svg/symbols.svg#close" />
</svg>
<span class="slds-assistive-text">Close</span>
</button>
<h2 id="modal-heading-01" class="slds-text-heading_medium slds-hyphenate">Modal Header</h2>
</header>
<div class="slds-modal__content slds-p-around_medium" id="modal-content-id-1">
</div>
<footer class="slds-modal__footer">
<button class="slds-button slds-button_neutral">Cancel</button>
<button class="slds-button slds-button_brand">Save</button>
</footer>
</div>
</section>
<div class="slds-backdrop slds-backdrop_open"></div>
</div>

Show and hide this model from button action.