Adding a CSS style with ::after to a text field

Hi,

I am trying to apply the following style to a Vaadin text field, which adds superscript text in an "::after" element:

.mystyle::after {
        content: "superscript text";
        vertical-align: super;
        font-size: 80%;
        color: gray;
        font-style: italic;
    }

I can call "textField.addStyleName("myStyle")", and the style name shows up correctly in the DOM, but the ::after element is not displayed in the browser (and also not in the DOM view). Why?
 

... it's a problem of HTML: input components (such as text fields) do not support CSS ::after styles.