to work this with unicode or fontawesome, you should add a span with class like below, because input tag not support pseudo classes like :after. this is not a direct solution
in html:
<span class="button1 search"></span>
<input name="username">
in css:
.button1 {
background-color: #B9D5AD;
border-radius: 0.2em 0 0 0.2em;
box-shadow: 1px 0 0 rgba(0, 0, 0, 0.5), 2px 0 0 rgba(255, 255, 255, 0.5);
pointer-events: none;
margin:1px 12px;
border-radius: 0.2em;
color: #333333;
cursor: pointer;
position: absolute;
padding: 3px;
text-decoration: none;
}